JP4045338B2 - Steering control method for four-wheel independent steering vehicle - Google Patents

Description

・・・・・式（Ｅ１１）

・・・・・式（Ｅ１２）

・・・・式（Ｅ１３）
操舵モードＭ２に対して：

・・・・・式（Ｅ２１）

・・・・・式（Ｅ２２）
操舵モードＭ３に対して：

・・・・・式（Ｅ３１）

・・・・・式（Ｅ３２）

・・・・・式（Ｅ３３）

・・・・・式（Ｅ３４）
操舵モードＭ４に対して：
右旋回時において、

・・・・・式（Ｅ４１）

・・・・・式（Ｅ４２）

・・・・・式（Ｅ４３）

・・・・式（Ｅ４４）
左旋回時において、

・・・・・式（Ｅ４５）

・・・・・式（Ｅ４６）

・・・・・式（Ｅ４７）

・・・・・式（Ｅ４８）
操舵モードＭ５に対して：
右旋回時において、

・・・・・式（Ｅ５１）

・・・・・式（Ｅ５２）

・・・・・式（Ｅ５３）

・・・・式（Ｅ５４）
左旋回時において、

・・・・・式（Ｅ５５）

・・・・・式（Ｅ５６）

・・・・・式（Ｅ５７）

・・・・・式（Ｅ５８）
但し、上記条件式において、
α_１は右前車輪に対する操舵角度．
α_２は左前車輪に対する操舵角度．
α_３は右後車輪に対する操舵角度．
α_４は左後車輪に対する操舵角度．
ｎ_１は右前車輪に対する回転速度．
ｎ_２は左前車輪に対する回転速度．
ｎ_３は右後車輪に対する回転速度．
ｎ_４は左後車輪に対する回転速度．
Ｌは前車輪と後車輪の間の中心線Ｘと各車輪の間の距離．
Ｗは右車輪と左車輪の間の中心線Ｙと各車輪の間の距離．
Ｒは各車輪の旋回軌跡が同心円弧となる場合の、同心円弧の中心と、各車輪の位置に対する中心点の間の距離．（車両の中心から車両の旋回中心までの距離、すなわち車両の回転半径）
【０００５】
しかしながら、車両の進行方向を変えるために、距離（車両の回転半径）Ｒを操舵指令値として、操舵指令値Ｒの設定値を増加あるいは減少させることにより、上記の条件式に従って各車輪の操舵角度α_１，α_２，α_３，α_４を減少あるいは増加させて車両の進行方向を変える場合、操舵指令値Ｒを現在の操舵指令値Ｒ_１から所望の操舵指令値Ｒ_２へ設定を変えても、各車輪の操舵角度α_１，α_２，α_３，α_４が上記条件式で規定される新たな操舵角度に到達する迄に若干の時間差（操舵指令追随時間）が生ずることから、その操舵指令追随時間の間の操舵過程において、左右両車輪の相互の向きが車両の進行方向に対し先拡がり状態となる開脚現象や、左右両車輪の相互の向きが車両の進行方向に対し先すぼみ状態となる閉脚現象が生ずる惧れがある。なお、開脚現象と閉脚現象を総じて開閉脚現象という。そして操舵過程において開閉脚現象が生ずると、操舵機構に無理な力が加わって故障の原因になる上に、車両上の人や物の安定が損なわれて危険を伴う。
【０００６】
また、実際に車両に乗車して操舵する運転者にとって車輪の操舵角度（車両の走行方向）と距離Ｒの間の物理的関係を直感的・体感的に捉えることが難しい上に、距離Ｒは、車両の直進方向を境にその左右で−∞から＋∞へ、あるいは＋∞から−∞へと不連続に反転することから、このような不連続に変化する距離Ｒを、操舵角度α_１，α_２，α_３，α_４の操舵指令値、すなわち操舵角度設定パラメータとして用いることは運転実務上好ましいとは言えない。
【０００７】
【特許文献１】
特願２００１−３５１１２７号特許出願明細書
【０００８】
【発明が解決しようとする課題】
この発明は、上記のような操舵上の問題点に鑑み、４輪独立操舵車両の操舵過程において車輪の開閉脚現象が生じないようにすると共に、車両の回転（旋回）半径に相当する距離Ｒに代わる操舵指令値を用いることにより、すなわち操舵指令値と車両走行方向の物理的関係が、車両を運行する運転者の操舵感覚に照らして分かり易くなる操舵指令値を用いることにより、運転者の操舵操作の錯覚を防ぎ、所望の方向へ迅速的確に操舵できるようにしようとするものである。また、車両の停止時から走行始動する際、あるいは操舵モードの変更時に、車両に衝撃が及ぶことを防止し、また車両が意図しない方向に始動・走行することがないようにしようとするものである。
【０００９】
【課題を解決するための手段】
この発明は、上記の課題を解決して目的を達するために、次のような各種の手段を用いる。
【００１０】
この発明は、４輪独立操舵車両の操舵過程で車輪の開閉脚現象が生じないようにするために、操舵指令値を変えることにより所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４を個別に制御して車両の走行方向を変える操舵制御において、操舵拘束条件式の中の一つの変数を操舵指令値Ｓとし、その操舵指令値ＳをＳ_１からＳ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｓ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から操舵指令値Ｓ_２に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ移行する過程で、操舵指令値Ｓ_１に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_{４］Ｓ１＋ΔＳ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｓ_１＋ΔＳ）に更に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋２ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］Ｓ_１＋２ΔＳ を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値ΔＳを順次加えた操舵指令値（Ｓ_１＋ｎΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ変化させることにより４輪独立操舵車両の操舵制御を行う。
【００１１】
また、車輪の駆動モータが同期モータあるいは誘導モータの場合、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に変化させて操舵制御する。すなわち、操舵指令値を変えることにより所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に制御して車両の走行方向を変える操舵制御において、操舵拘束条件式中の一つの変数を操舵指令値Ｓとし、その操舵指令値ＳをＳ_１からＳ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｓ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から操舵指令値Ｓ_２へ対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ に移行する過程で、操舵指令値Ｓ_１に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ３，ｎ４］_{Ｓ１＋ΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｓ_１＋ΔＳ）に更に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋２ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋２ΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋２ΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値ΔＳを順次加えた操舵指令値_{（Ｓ１＋ｎΔＳ）}に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ｎΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ｎΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ変化させることにより４輪独立操舵車両の操舵制御を行う。
【００１２】
そして実際に用いる操舵指令値の例として、各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離Ｒを操舵指令値として用いる。すなわち、操舵指令値を変えることにより所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４を個別に制御して車両の走行方向を変える操舵制御において、各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離Ｒを操舵指令値とし、その操舵指令値ＲをＲ_１からＲ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｒ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から操舵指令値Ｒ２に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ移行する過程で、操舵指令値Ｒ１に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｒ_１＋ΔＲ）に更に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋２ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値ΔＲを順次加えた操舵指令値（Ｒ_１＋ｎΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ変化させることにより４輪独立操舵車両の操舵制御を行う。
【００１３】
また、車輪の駆動モータが同期モータあるいは誘導モータの場合、各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離Ｒを操舵指令値とし、その操舵指令値ＲをＲ_１からＲ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｒ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から操舵指令値Ｒ_２に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ移行する過程で、操舵指令値Ｒ_１に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ΔＲ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｒ_１＋ΔＲ）に更に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋２ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋２ΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋２ΔＲ} に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が操舵整合したことを検知した後、微小操舵指令値ΔＲを順次加えた操舵指令値（Ｒ_１＋ｎΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ｎΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ｎΔＲ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ変化させることにより輪独立操舵車両の操舵制御を行う。
【００１４】
また、特に多用されると考えられる所定の操舵モードの例として、右後車輪の走行軌跡と左後車輪の走行軌跡がそれぞれ右前車輪の走行軌跡と左前車輪の走行軌跡に追従する操舵モード（略して「操舵モードＭ１」という）と、前車輪の旋回軌跡に対し後車輪の旋回軌跡がいわゆる内輪差軌跡となる操舵モード（略して「操舵モードＭ３という」について、操舵モードを形成する操舵拘束条件式を明示する。
【００１５】
すなわち、各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離Ｒを操舵指令値とした場合、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する操舵角度をα_１，α_２，α_３，α_４とし、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度をｎ_１，ｎ_２，ｎ_３，ｎ_４とし、前車輪と後車輪の間の中心線Ｘと各車輪の間の距離をＬとし、右車輪と左車輪の間の中心線Ｙと各車輪の間の距離をＷとして、
操舵モードＭ１を形成する操舵拘束条件式を、

で表すことができる条件式とし、
操舵モードＭ３を形成する操舵拘束条件式を、

で表すことができる条件式とする。
なお、操舵制御にあたり右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を強制制御する必要がない場合は、上記のｎ_１：ｎ_２：ｎ_３：ｎ_４に関する条件式は不要である。
【００１６】
またこの発明は、操舵指令値を運転者の操舵方向感覚に適合したものとして運転者の操舵操作の錯覚を防ぎ所望の方向への操舵を確実に実行できるようにするために、上記の操舵指令値Ｒ（車両の回転半径に相当する距離Ｒ）に代わる操舵指令値として、車両上の任意の点Pnの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_ｎ、あるいは左右の前車輪を結ぶ直線の中点Poの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_０を用いる。
【００１７】
すなわち、この発明は、操舵指令値の取り方を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４を個別に制御して車両の走行方向を変える操舵制御において、車両上の任意の点Pnの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_ｎを操舵指令値とし、その操舵指令値α_ｎをα_ｎ１からα_ｎ２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値α_ｎ１に対応する各操舵角度［α_１，α_２，α_３，α_４］_αｎ１ から操舵指令値α_ｎ２に対応する各操舵角度［α_１，α_２，α_３，α_４］_αｎ２ へ移行する過程で、操舵指令値α_ｎ１に微小操舵指令値Δα_ｎを加えた操舵指令値（α_ｎ１＋Δα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}に到達して舵角整合したことを検知した後、前記操舵指令値（α_ｎ１＋Δα_ｎ）に更に微小操舵指令値Δα_ｎを加えた操舵指令値（α_ｎ１＋２Δα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋２Δαｎ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋２Δαｎ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値Δα_ｎを順次加えた操舵指令値（α_ｎ１＋ｎΔα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ}に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_αｎ１ から各操舵角度［α_１，α_２，α_３，α_４］_αｎ２ へ変化させることにより４輪独立操舵車両の操舵制御を行う。
【００１８】
あるいはまた、操舵指令値の取り方を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に制御して車両の走行方向を変える操舵制御において、車両上の任意の点Pnの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_ｎを操舵指令値とし、その操舵指令値α_ｎをα_ｎ１からα_ｎ２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値α_ｎ１に対応する各操舵角度［α_１，α_２，α_３，α_４］_αｎ１ から操舵指令値α_ｎ２に対応する各操舵角度［α_１，α_２，α_３，α_４］_αｎ２ へ移行する過程で、操舵指令値α_ｎ１に微小操舵指令値Δα_ｎを加えた操舵指令値（α_ｎ１＋Δα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ＋Δαｎ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ１＋Δαｎ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋Δαｎ}に到達して舵角整合したことを検知した後、前記操舵指令値（α_ｎ１＋Δα_ｎ）に更に微小操舵指令値Δα_ｎを加えた操舵指令値（α_ｎ１＋２Δα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋２Δαｎ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ１＋２Δαｎ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋２Δαｎ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ１＋２Δαｎ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵司令値Δα_ｎを順次加えた操舵指令値（α_ｎ１＋ｎΔα_ｎ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ１＋ｎΔαｎ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ}とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{αｎ１＋ｎΔαｎ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋ｎΔαｎ}に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_αｎ１ から各操舵角度［α_１，α_２，α_３，α_４］_αｎ２ ヘ変化させることにより４輪独立操舵車両の操舵制御を行う。
【００１９】
そして、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する操舵角度をα_１，α_２，α_３，α_４とし、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度をｎ_１，ｎ_２，ｎ_３，ｎ_４とし、前車輪と後車輪の間の中心線Ｘと各車輪の間の距離をＬとし、右車輪と左車輪の間の中心線Ｙと各車輪の間の距離をＷとし、車両上の任意の点PnのＸ座標をｘ_ｎ，Ｙ座標をｙ_ｎとし、点Pnの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度をα_ｎとし、角度α_ｎを操舵指令値として、所定の操舵モードＭ１を形成する操舵拘束条件式を、

で表すことができる条件式とし、
所定の操舵モードＭ３を形成する操舵拘束条件式を、

で表すことができる条件式とする。
なお、操舵制御にあたり右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を強制制御する必要がない場合は、上記のｎ_１：ｎ_２：ｎ_３：ｎ_４に関する条件式は不要である。
【００２０】
またこの発明は、操舵指令値の取り方を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４を個別に制御して車両の走行方向を変える操舵制御において、左右の前車輪を結ぶ直線の中点P0の移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_０を操舵指令値とし、その操舵指令値α_０をα_０１からα_０２へ変えて各操舵角度α_１，α_２，α_３，α_４を、操舵指令値α_０１に対応する各操舵角度［α_１，α_２，α_３，α_４］_α０１ から操舵指令値α_０２に対応する各操舵角度［α_１，α_２，α_３，α_４］_α０２へ移行する過程で、操舵指令値α_０１に微小操舵指令値Δα_０を加えた操舵指令値（α_０１＋Δα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０}に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０} に到達して舵角整合したことを検知した後、前記操舵指令値（α_０１＋Δα_０）に更に微小操舵指令値Δα_０を加えた操舵指令値（α_０１＋２Δα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{αｎ１＋２Δα０}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋２Δα０}に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、以後同様に、各車輪の各操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値Δα_０を順次加えた操舵指令値（α_０１＋ｎΔα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０}に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０}に到達して舵角整合したことの検知を繰り返して，各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_α０１ から各操舵角度［α_１，α_２，α_３，α_４］_α０２ へ変えることにより４輪独立操舵車両の操舵制御を行なう。
【００２１】
あるいはまた、操舵指令値の取り方を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に制御して車両の走行方向を変える操舵制御において、左右の前車輪を結ぶ直線の中点Poの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_０を操舵指令値とし、その操舵指令値α_０をα_０１からα_０２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値α_０１に対応する各操舵角度［α_１，α_２，α_３，α_４］_α０１ から各操舵指令値α_０２に対応する各操舵角度［α_１，α_２，α_３，α_４］_α０２ へ移行する過程で、操舵指令値α_０１に微小操舵司令値Δα_０を加えた操舵司令値（α_０１＋Δα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋Δα０}を演算し，その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋Δα０}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋Δα０} に到達して舵角整合したことを検知した後、前記操舵指令値（α_０１＋Δα_０）に更に微小操舵指令値Δα_０を加えた操舵指令値（α_０１＋２Δα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋２Δα０} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋２Δα０}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋２Δα０} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋２Δα０}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値Δα_０を順次加えた操舵指令値（α_０１＋ｎΔα_０）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋ｎΔα０}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{α０１＋ｎΔα０}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{α０１＋ｎΔα０}に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_α０１ から各操舵角度［α_１，α_２，α_３，α_４］_α０２ へ変えることにより４輪独立操舵車両の操舵制御を行なう。
【００２２】
そして、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する操舵角度をα_１，α_２，α_３，α_４とし、右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度をｎ_１，ｎ_２，ｎ_３，ｎ_４とし、前車輪と後車輪の間の中心線Ｘと各車輪の間の距離をＬとし、右車輪と左車輪の間の中心線Ｙと各車輪の間の距離をＷとし、左右の前車輪を結ぶ直線の中点Poの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度をα_０とし、角度α_０を操舵指令値として、所定の操舵モードＭ１を形成する操舵拘束条件式を、

で表すことができる条件式とし、
所定の操舵モードＭ３を形成する操舵拘束条件式を、

で表すことができる条件式とする。
なお、操舵制御にあたり右前車輪、左前車輪、右後車輪、左後車輪のそれぞれに対する回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を強制制御する必要がない場合は、上記のｎ_１：ｎ_２：ｎ_３：ｎ_４に関する条件式は不要である。
【００２３】
さらにこの発明は、車両が停止状態から走行始動する際、あるいは操舵モードの変更時に、車両の走行に衝撃が生ずることなく車両を所定の操舵モードで所望に方向へ正しく円滑に始動させ走行させるために、車両の前進・後進モードを含む複数種類の操舵モードにおける操舵モード変更時に、各車輪の操舵角度α_１，α_２，α_３，α_４を一旦α_１＝α_２＝α_３＝α_４＝０の直進方向にリセットした後に、所定の操舵モードを形成する操舵拘束条件式に従って各操舵角度α_１，α_２，α_３，α_４を個別に変化させる。
【００２４】
そしてまた、車両の前進・後進モードを含む複数種類の操舵モードの中から任意に選択される所定の操舵モードを変更する際には、各車輪の操舵角度α_１，α_２，α_３，α_４が、操舵モード変更後の操舵拘束条件式を満たした後に、車両を走行駆動する。
【００２５】
【発明の実施の形態】
この発明の基本的な実施形態の一つは、操舵指令値を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４を個別に制御して車両の走行方向を変える操舵制御において、操舵拘束条件式中の一つの変数を操舵指令値Ｓとし、その操舵指令値ＳをＳ_１からＳ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｓ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］Ｓ_１ から操舵指令値Ｓ２に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ移行する過程で、操舵指令値Ｓ_１に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｓ_１＋ΔＳ）に更に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋２ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値ΔＳを順次加えた操舵指令値（Ｓ_１＋ｎΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ変化させる４輪独立操舵車両の操舵制御方法である。
【００２６】
また、この発明の基本的な他の実施形態は操舵指令値の取り方を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に制御して車両の走行方向を変える操舵制御において、操舵拘束条件式中の一つの変数を操舵指令値Ｓとし、その操舵指令値ＳをＳ_１からＳ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｓ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から操舵指令値Ｓ_２へ対応する各操舵角度［α_１，α_２，α_３，α_４］Ｓ_２ に移行する過程で、操舵指令値Ｓ_１に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｓ_１＋ΔＳ）に更に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋２ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ２＋２ΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋２ΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋２ΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が舵角整合したことを検知した後、微小操舵指令値ΔＳを順次加えた操舵指令値（Ｓ_１＋ｎΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ｎΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｓ１＋ｎΔＳ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α１，α２，α３，α４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ変化させる４輪独立操舵車両の操舵制御方法である。
【００２７】
【実施例】
以下この発明を、その実施例を示す図面を参考に説明する。図１はこの発明に係る電気移動車両の車体ベースの基本構成を示す平面図、図２は同車体ベースに装着される車輪操舵・駆動ブロックの斜視図である。図１において、１は電気移動車両の車体ベースで、点Ｐ１，Ｐ２は車体ベース１の下面に装着される左右二つの前車輪の位置を示し、点Ｐ３，Ｐ４は車体ベース１の下面に装着される左右二つの後車輪の位置を示すものである。また、２１は右前車輪、２２は左前車輪、２３は右後車輪、２４は左後車輪をそれぞれ示し、矢印Ｎは車両の前方直進方向を示している。点Ｐ１，Ｐ２，Ｐ３，Ｐ４の位置（車輪２１，２２，２３，２４の位置）は長方形の各頂点の位置にあって、Ｏはその長方形の中心点、すなわち各点Ｐ１，Ｐ２，Ｐ３，Ｐ４に対する中心点である。換言すればすなわち、図１，３からも明らかなように、各車輪の位置Ｐ１，Ｐ２，Ｐ３，Ｐ４に対する中心点Ｏは、四つの各車輪の位置Ｐ１、Ｐ２，Ｐ３，Ｐ４を頂点とする長方形の中心点、すなわち四つの各車輪位置から等距離にある点を意味する。Ｘ軸とＹ軸は中心点Ｏを通る直交座標軸でこの発明を説明するために仮想設定したものである。そしてＸ軸は前車輪２１，２２と後車輪２３，２４の間の中心線（車両の左右方向の中心線）であり、Ｙ軸は右車輪２１，２３と左車輪２２，２４の間の中心線（車両の前後方向の中心線）である。なおＹ軸の方向は前記矢印Ｎに示す車両の前方直進方向と同じであり、Ｈ１は点Ｐ１，Ｐ２を結ぶ前車輪軸線で前車輪２１，２２の仮想車軸に相当し、Ｈ２は点Ｐ３，Ｐ４を結ぶ後車輪軸線で後車輪２３，２４の仮想車軸に相当する。ＬはＸ軸から各点Ｐ１，Ｐ２，Ｐ３，Ｐ４までの距離、ＷはＹ軸から各点Ｐ１，Ｐ２，Ｐ３，Ｐ４までの距離である。また、Ｐ０は右前車輪の位置Ｐ１と左前車輪の位置Ｐ２を結ぶ直線の中点を示している。さらにまた、Ｐｎは車体ベース１上の任意の点で、例えば車両の運転者が立つ位置であり、点Ｐｎの位置は直交座標軸Ｘ，Ｙに対する座標（Ｘ座標：xn，Ｙ座標：yn）で示されている。Ａ０は車両の走行に伴う点Ｐ０の移動方向を示し、α０は点Ｐ０の移動方向Ａ０が車両の中心線Ｙとなす角度（操舵に伴う中点Ｐ０の移動方向角度）を示している。Ａｎは車両の走行に伴う点Ｐｎの移動方向を示し、αｎは点Ｐｎの移動方向Ａｎが車両の中心線Ｙとなす角度（操舵に伴う点Ｐｎの移動方向角度）を示している。
【００２８】
ｎ_１，ｎ_２，ｎ_３，ｎ_４は、それぞれ右前車輪２１，左前車輪２２，右後車輪２３，左後車輪２４の回転速度を表し、α_１，α_２，α_３，α_４は、それぞれ車両の操舵制御時における右前車輪２１，左前車輪２２，右後車輪２３，左後車輪２４の操舵角度を表している。なお、A1，A2，A3，A4は、それぞれ車両の操舵制御時における右前車輪２１，左前車輪２２，右後車輪２３，左後車輪２４の向き（走行向き）を表している。
【００２９】
車両の操舵制御時における各車輪２１，２２，２３，２４の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４とその操舵角度α_１，α_２，α_３，α_４は、それぞれ個別に独立制御されるもので、そのために図２に示すように、前車輪２１，２２と後車輪２３，２４のそれぞれに回転速度制御用の駆動モータ２１ａ，２２ａ，２３ａ，２４ａと操舵角度制御用の操舵モータ２１ｂ，２２ｂ，２３ｂ，２４ｂが連結されて個別の操舵・駆動ブロックB1，B2，B3，B4が形成されている。また、車両の走行制御時における各車輪２１，２２，２３，２４の実際の走行向き（実際の操舵角度）を操舵角度センサーで検出し、その検出信号を制御系にフィードバックして、運転者が設定した操舵指令値に対応する操舵角度α_１，α_２，α_３，α_４通りの操舵制御が維持されるようにしている。また、上記の車両に対して、操舵モードＭ１，Ｍ２，Ｍ３，Ｍ４，Ｍ５の操舵モードが用意され、各操舵モードを形成するために必要な各車輪の操舵角度と回転速度を算出する演算プログラムを備えた演算手段（コンピュータ）が電気移動車両に組み込まれている。なお、車輪の駆動モータには、直流モータ、同期モータ、誘導モータ４などが用いられるが、４個の駆動モータに同一仕様の直流モータを採用しこれらを直列接続とする場合は、４個の駆動モータの電気回路的な相補作用により、車輪の空転が無い限り、回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_３，ｎ_４の比は拘束条件式を自動的に満たすので、駆動モータを個別に独立制御する必要はない。
【００３０】
操舵モードＭ１は、図３に示すように、前車輪の操舵角度α_１，α_２と後車輪の操舵角度α_３，α_４を互いに車両の進行方向に対し左右逆方向に切って左右の後車輪の軌跡がそれぞれ左右の前車輪の軌跡に追従する操舵モードである。なお図３において、点P5（Ｘ座標：Ｒ，Ｙ座標：０）は車両の右回り旋回（時計回り旋回）（ＣＷ）時の中心となる点を示し、点P6（Ｘ座標：−Ｒ，Ｙ座標：０）は車両の左回り旋回（反時計回り旋回）（ＣＣＷ）時の中心となる点を示している。操舵モードＭ１においては、図３に示されるように、各車輪の旋回軌跡は同心円弧となるが、点P5，P6 はその同心円弧の中心となる点でもある。そして図３に照らせば明らかなように、操舵モードＭ１で走行するためには、操舵角度α_１，α_２が次の表１に示す条件下において、各車輪２１，２２，２３，２４の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４について，次の操舵拘束条件式（条件式）（Ｅ１１），（Ｅ１２），（Ｅ１３）が満たされ維持されなければならない。
【００３１】
【表１】

【００３２】

・・・・・式（Ｅ１１）

・・・・・式（Ｅ１２）

・・・・・式（Ｅ１３）
【００３３】
操舵モードＭ２は、図４に示すように、前車輪の操舵角度α_１，α_２と後車輪の操舵角度α_３，α_４を共に同方向同角度に切って前車輪と後車輪の軌跡を全て平行パターンとし車両が左右・斜めに平行的に移動する操舵モードである。そして図４に照らせば明らかなように、操舵モードＭ２で走行するためには、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４について次の条件式（Ｅ２１），（Ｅ２２）が満たされ維持されなければならない。
【００３４】

・・・・・式（Ｅ２１）

・・・・・式（Ｅ２２）
【００３５】
操舵モードＭ３は、図５に示すように、前車輪の操舵角度α_１，α_２のみを操舵する従来の自動車と同様の操舵モードで、前車輪と後車輪相互の軌跡は、いわゆる内輪差軌跡を描く操舵モードである。そして図５に照らせば明らかなように、操舵モードＭ３では、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４について、次の条件式（Ｅ３１），（Ｅ３２），（Ｅ３３），（Ｅ３４）が満たされ維持されている。なお図５に示されるように、操舵モードＭ３における右旋回の中心となる点P5’と左旋回の中心となる点P6’は、それぞれ後車輪軸線H2に対し距離ｄだけ離れているが、車両の速度が低い場合にはｄ≒０とみることができる。
【００３６】

・・・・・式（Ｅ３１）

・・・・・式（Ｅ３２）

・・・・式（Ｅ３３）

・・・・式（Ｅ３４）
但し、

なお、車両は低速で走行するので、ｄ＝０とする。
【００３７】
操舵モードＭ４は、図６に示すように、右後車輪（点P3）を中心として車両を右回り旋回（時計回り旋回）（ＣＷ）させ、あるいは左後車輪（点P4）を中心として車両を左回り旋回（反時計回り旋回）（ＣＣＷ）させる操舵モードである。そして図６に照らせば明らかなように、操舵モードＭ４の走行では、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４について次の条件式（Ｅ４１），（Ｅ４２），（Ｅ４３），（Ｅ４４），（Ｅ４５），（Ｅ４６），（Ｅ４７），（Ｅ４８）が満たされ維持されなければならない。
【００３８】
すなわち、右後車輪（点P3）を回転中心として車両を時計回り方向（ＣＷ）に旋回させるとき、

・・・・・式（Ｅ４１）

・・・・・式（Ｅ４２）

・・・・・式（Ｅ４３）

・・・・・式（Ｅ４４）
但し、

【００３９】
すなわち、左後車輪（点P4）を回転中心として車両を反時計回り方向（ＣＣＷ）に旋回させるとき、

・・・・式（Ｅ４５）

・・・・・式（Ｅ４６）

・・・・・式（Ｅ４７）

・・・・・式（Ｅ４８）
但し、

【００４０】
操舵モードＭ５は、図７に示すように、右前車輪（点P1）を中心として車両を右回り（時計回り）（ＣＷ）させ、あるいは左前車輪（点P2）を中心として車両を左回り（反時計回り）（ＣＣＷ）に旋回させる操舵モードである。そして図７に照らせば明らかなように、操舵モードＭ５の走行では、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４について次の条件式（Ｅ５１），（Ｅ５２），（Ｅ５３），（Ｅ５４），（Ｅ５５），（Ｅ５６），（Ｅ５７），（Ｅ５８）が維持されなければならない。
【００４１】
すなわち、右前車輪（点P1）を回転中心として車両を時計回り（ＣＷ）に旋回させるとき、

・・・・・式（Ｅ５１）

・・・・・式（E5２）

・・・・・式（Ｅ５３）

・・・・・式（Ｅ５４）
但し、

【００４２】
すなわち、左前車輪（点P2）を回転中心として車両を反時計回り（ＣＣＷ）に旋回させるとき、

・・・・・式（Ｅ５５）

・・・・式（Ｅ５６）

・・・・・式（Ｅ５７）

・・・・・式（Ｅ５８）
但し、

【００４３】
このようにそれぞれの操舵モードＭ１，Ｍ２，Ｍ３，Ｍ４，Ｍ５において四つの各車輪が辿る軌跡が同じでないことから、各軌跡の円弧長に合わせた回転速度で車輪を駆動しなければならず、各車輪２１，２２，２３，２４の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４は、操舵遷移中も操舵終了後においても、車両の進行速度および進行方向の指令と、操舵モードによって決定される各条件式（Ｅ１１）〜（Ｅ５８）の条件を満たすように制御されなければならない。そしてこの条件が満たされない場合には、車輪の空転やスリップが生じたり、左右の車輪の間に開閉脚現象が生ずる。
【００４４】
したがって車両には、操舵モードＭ１に沿う操舵に必要な操舵拘束条件式（Ｅ１１）（Ｅ１２）に基づいて各車輪の操舵角度α_１，α_２，α_３，α_４ を演算する演算プログラム、操舵モードＭ２に沿う操舵に必要な操舵拘束条件式（Ｅ２１）に基づいて各車輪の操舵角度α_１，α_２，α_３，α_４ を演算する演算プログラム、操舵モードＭ３に沿う操舵に必要な操舵拘束条件式（Ｅ３１），（Ｅ３２），（Ｅ３３）に基づいて各車輪の操舵角度α_１，α_２，α_３，α_４ を演算する演算プログラム、操舵モードＭ４に沿う操舵に必要な操舵拘束条件式（Ｅ４１），（Ｅ４２），（Ｅ４３），（Ｅ４５），（Ｅ４６），（Ｅ４７）に基づいて各車輪の操舵角度α_１，α_２，α_３，α_４ を演算する演算プログラム、操舵モードＭ５に沿う操舵に必要な操舵拘束条件式（Ｅ５１），（Ｅ５２），（Ｅ５３），（Ｅ５５），（Ｅ５６），（Ｅ５７）に基づいて各車輪の操舵角度α１，α２，α３，α４ を演算する演算プログラムが記憶された車輪操舵角度演算手段が搭載されている。
【００４５】
また車両には、操舵モードＭ１に沿う操舵に必要な操舵拘束条件式（Ｅ１３）に基づいて各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４ を算出する演算プログラム、操舵モードＭ２に沿う操舵に必要な操舵拘束条件式（Ｅ２２）に基づいて各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４ を算出する演算プログラム、操舵モードＭ３に沿う操舵に必要な操舵拘束条件式（Ｅ３４）に基づいて各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４ を算出する演算プログラム、操舵モードＭ４に沿う操舵に必要な操舵拘束条件式（Ｅ４４），（Ｅ４８）に基づいて各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４ を算出する演算プログラム、操舵モードＭ５に沿う操舵に必要な操舵拘束条件式（Ｅ５４），（Ｅ５８）に基づいて各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４ を演算する演算プログラムが記憶された車輪回転速度演算手段が搭載されている。
【００４６】
この発明は、車両の走行中すなわち４輪独立操舵車両の操舵過程で常に上記の操舵拘束条件式を満たすように制御して車輪の開閉脚現象を防止するものであるが、そのために先ず、各車輪の操舵角度α_１，α_２，α_３，α_４を設定し変更するための「操舵指令値」について考える必要がある。
【００４７】
例えば操舵モードＭ１では、先に記したように、操舵角度α_１，α_２，α_３，α_４が式（Ｅ１１），式（Ｅ１２）によって定められる。

・・・・・式（Ｅ１１）

・・・・式（Ｅ１２）
ここで、変数はα_１，α_２，α_３，α_４とＲの５個で式は４個存在するから、変数のうちの一つを決めれば他の四つの変数は一義的に決まる。そして、距離Ｌと距離Ｗは車両設計によって決まっているから、距離Ｒを決めることにより操舵角度α_１，α_２，α_３，α_４は一義的に決まる。従って、距離（車両の回転半径）Ｒが「操舵指令値」として用いられてきた。
【００４８】
また、例えば操舵モードＭ３では、先に記したように、操舵角度α_１，α_２，α_３，α_４が式（Ｅ３１），式（Ｅ３２），式（Ｅ３３）によって定められる。

・・・・・式（Ｅ３１）

・・・・・式（Ｅ３２）

・・・・式（Ｅ３３）
ここで、変数はα_１，α_２とＲの３個で式は２個存在するから、変数のうちの一つを決めれば他の二つの変数は一義的に決まる。そして、距離Ｌと距離Ｗは車両設計によって決まっているから、距離Ｒを決めることにより操舵角度α_１，α_２，α_３，α_４は一義的に決まる。従って、距離（車両の回転半径）Ｒが「操舵指令値」として用いられてきた。
【００４９】
ここでW=0.5m，L=1mとして、距離Ｒと操舵角度α_１，α_２，α_３，α_４の値を求めると、操舵モードＭ１では図８に示す特性となり、操舵モードＭ３では図９に示す特性となる。次に操舵モードＭ１を例にとって、Ｒ＝１ｍからＲ＝２ｍに操舵したときの操舵角度α_１，α_２の変化を図８から調べると、操舵角度α_１は63.2度から33.7度に変化してその変化幅は63.2−33.7=29.5度であり、操舵角度α_２は33.7度から21.8度に変化してその変化幅は33.7−21.8=11.9度であることが分かる。そこで若し操舵角度α_１と操舵角度α_２とが同じ角速度で回転したとすれば、操舵角度α_２が目標値に達した時に操舵角度α_１は未だ目標値に向けての回転途上にあることになり、進行方向に対して左右の車輪が先拡がりの状態となって開脚現象が生ずる。また、Ｒ＝１ｍからＲ＝２ｍに操舵したときは、これとは逆の閉脚現象が生ずる。開閉脚現象が生ずると、操舵機構に無理が加わるのみならず、車両に乗っている人は前のめりになって危険なので開閉脚現象が生じないようにしなければならない。そして開閉脚現象を防止するためには、車両が動いている総ての時間断面において、条件式の式（Ｅ１１），式（Ｅ１２）が満たされていなければならないことが分かる。このことは操舵モードＭ１のみならず操舵モードＭ２，Ｍ３，Ｍ４，Ｍ５ついても同様である。このように車両の各車輪の操舵角度（各車輪の走行向き）がそれぞれの操舵拘束条件式を満たす角度になることを、本願においては、「舵角整合」という。
【００５０】
舵角整合を実現させる一つの方法は、運転者が操舵指令値となる距離Ｒを変えて新たな操舵指令値（距離）を設定し操舵角度α_１，α_２，α_３，α_４を変える際に、操舵指令値（距離）Ｒを徐々に変化させながら、その時々に操舵拘束条件式を満たす操舵角度を演算して操舵角度α_１，α_２，α_３，α_４を徐々に変化させ、若干の操舵指令追随時間の後に、操舵指令値（距離）Ｒを上記の新たに設定した操舵指令値（変更後の操舵指令目標値）に導くと共に、操舵角度α_１，α_２，α_３，α_４を上記の新たに設定した操舵指令値に対応する所期の操舵角度へ移行させることである。
【００５１】
すなわち、操舵指令値を変えることにより、所定の操舵モードを形成する操舵拘束条件式に従って車両の四つの車輪の各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を個別に制御して車両の走行方向を変える操舵制御において、各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離Ｒを操舵指令値とし、その操舵指令値ＲをＲ_１からＲ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｒ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から操舵指令値Ｒ_２に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ移行する過程で、操舵指令値Ｒ_１に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ΔＲ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ΔＲ} に到達して舵角整合したことを検知した後、前記操舵指令値（Ｒ_１＋ΔＲ）に更に微小操舵指令値ΔＲを加えた操舵指令値（Ｒ_１＋２ΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋２ΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋２ΔＲ} とその微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋２ΔＲ} に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、以後同様に、各車輪の操舵角度α_１，α_２，α_３，α_４が操舵整合したことを検知した後、微小操舵指令値ΔＲを順次加えた操舵指令値（Ｒ_１＋ｎΔＲ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ}と微小移行回転速度［ｎ_１，ｎ_２，ｎ_３，ｎ_４］_{Ｒ１＋ｎΔＲ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} とその微小移行回転速度［ｎ１，ｎ２，ｎ３，ｎ４］_{Ｒ１＋ｎΔＲ}に向けて各操舵角度α_１，α_２，α_３，α_４と各回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｒ１＋ｎΔＲ} に到達して舵角整合したことの検知を繰り返して、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ各操舵角度［α_１，α_２，α_３，α_４］_Ｒ１ から各操舵角度［α_１，α_２，α_３，α_４］_Ｒ２ へ変えるものであり、この操舵制御方法がこの発明の特徴である。
【００５２】
次に操舵モードＭ１について、距離（車両の回転半径）（操舵指令値）Ｒに対する車輪の操舵角度αの感度を調べる。一般に次の公式（１），公式（２）があることから、条件式の式（Ｅ１１）は次のように展開できる。

のとき、

・・・・公式（１）

のとき、

・・・・・公式（２）

・・・・式（Ｅ１１）

・・・・・式（１）
同様に

・・・・・式（２）
ここで、式（１）、式（２）に、W=0.5m、L=1mを入れて計算した結果を、図１０に示す。図１０に示されるところから明らかなように、Ｒが小さい領域ではαのＲに対する感度は高く、また左右の車輪によって感度が違っていることが分かる。また操舵モードＭ３についても同様の計算をした結果を図１１に示すが、同様にＲが小さい領域でαのＲに対する感度は高く、左右の車輪によって感度が違っていることが分かる。
【００５３】
このように、車輪の操舵角度αの、距離（車両の回転半径すなわち操舵指令値）Ｒに対する感度は、Ｒの値によって大きく変わることから、距離（車両の回転半径）Ｒをそのまま操舵指令値とすることは適切ではない。そこで新たに距離Ｒと時間ｔの関数、Ｒ＝ｆ(ｔ)を導入し、その関数Ｒ＝ｆ(ｔ)を介して車輪の操舵角度αを制御することが考えられる。その場合の関数の導入過程は次の通りである。
【００５４】
式（１）を次のように変形する。

・・・・・式（３）
同様に

・・・・・式（４）
ここで

とするには（但し，Ｋ＝一定値）、

・・・・式（５）
したがって、

・・・・式（６）

・・・・式（７）
となる。ここで次の公式（３）を適用すれば式（１３）に至る。すなわち、

・・・・・公式（３）

・・・・式（８）

・・・・式（９）

・・・・式（１０）

・・・・・式（１１）
ここで、R=0，W=0.5，L=1，t=0 とすると、積分定数ＣＬは、CL=0.463648 (rad)となる。したがって、K=−π/20とすれば、

・・・・・式（１２）

・・・・式（１３）
すなわち、距離Ｒを式（１３）に示す時間ｔの関数として変化させればよい。このとき、右前車輪の操舵角度α_１、左前車輪の操舵角度α_２は、それぞれ次の式（１４）、式（１５）、式（１６）に示すようになる。

・・・・・式（Ｅ１１）

・・・・・式（１４）

・・・・・式（Ｅ１２）

・・・・・式（１５）

・・・・式（１６）
【００５５】
図１２は、時間ｔに対する距離Ｒ、右前車輪の操舵角度α_１、左前車輪の操舵角度α_２の変化を示しており、右前車輪の操舵角度αは時間ｔに対して直線的に変化することが分かる。このように、車両の前後方向の中心線Ｙから車両の回転中心までの距離Ｒを操舵指令値としたとき、Ｒの変化領域の中でｄα／ｄＲは大きく変化するので、これを一定にするような時間ｔと距離Ｒについての新しい関数R=f(t)（例えば操舵モードＭ１の場合、R=W+Ltan(−Kt+CL)）を導入し、時間ｔの関数として距離Ｒを制御し、その距離Ｒから操舵角度αを制御することによって良好な制御を実現することができる。
【００５６】
上述のように、距離Ｒを操舵指令値として用いると、理論展開の上ではシンプルとなるが、運転者が実際に操舵制御する場合には、運転者にとって操舵操作がやり難いことは否めない。すなわち、距離Ｒが小さい時と大きい時とでは感度ｄα／ｄＲが２桁以上も違い、実際の運転で頻度が高い直進方向近傍の操舵角度範囲において感度ｄα／ｄＲが過敏で、また距離Ｒが＋∞から−∞へ又−∞から＋∞へと不連続に反転し、さらに距離Ｒが車両の横方向の回転中心までの距離であるため運転者にとって実際の運転感覚と結び付き難いことから、運転者の操舵操作を難しくしている。
【００５７】
そこでこの発明では、左右の前車輪を結ぶ直線上の中点P0の移動方向が車両の中心線となす角度α_０を、距離Ｒに代えて、操舵指令値とするものである。
【００５８】
すなわち、例えば操舵モードＭ１（図３参照）においては、

・・・・式（１７）

・・・・式（１８）
式（１８）を前記の式（Ｅ１１），（Ｅ１２），（Ｅ１３）に代入すれば、各車輪の操舵角度α_１，α_２，α_３，α_４、および各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４の比は次式のようになる。

・・・・・式（１９）

・・・・式（２０）

・・・・・式（２１）
【００５９】
操舵モードＭ３（図５参照）においては、

・・・・式（２２）

・・・・式（２３）
式（２３）を前記の式（Ｅ３１），（Ｅ３２），（Ｅ３４）に代入すれば、各車輪の操舵角度α_１，α_２および各車輪の回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４の比は次式のようになる。

・・・・・式（２４）

・・・・式（２５）

・・・・式（２６）
【００６０】
また、Ｗ＝０．５ｍ，Ｌ＝１ｍとして、中点P0の移動方向が車両中心線Ｙとなす角度α_０と各車輪の操舵角度α１，α２，α３，α４の関係を求めると、操舵モードＭ１では図１３に示すようになり、操舵モードＭ３では図１４に示すようになる。このように、操舵制御の操舵指令値として、左右の前輪を結ぶ直線上の中点P0の移動方向が車両中心線Ｙとなす角度α_０を用いることによって、距離Ｒを操舵指令値として用いる場合に比し、制御系の過敏な特性と不連続特性の弊害を排し、運転者の実際の運転における車両走行方向感覚に沿った操舵制御を行うことができる。
【００６１】
更にまた、上記の中点P0に代えて、車両上の任意の点Pn（Ｘ座標：ｘ_ｎ，Ｙ座標：ｙ_ｎ）の移動方向が車両中心線Ｙとなす角度α_ｎを操舵指令値とすることもできる。（図３，図５参照）
【００６２】
車両上の任意の点Pn（Ｘ座標：ｘ_ｎ，Ｙ座標：ｙ_ｎ）の移動方向が車両中心線Ｙとなす角度α_ｎを操舵指令値とする場合、その角度α_ｎと点Pn座標（ｘ_ｎ，ｙ_ｎ）の間には次の関係がある。

・・・・・式（２７）

・・・・・式（２８）
【００６３】
そして操舵モードＭ１においては、上記の式（２８）を前記の式（Ｅ１１），（Ｅ１２），（Ｅ１３）に代入することにより、次式（２９），（３０），（３１）が導かれ、点Pnの移動方向角度（操舵指令値）α_ｎを基に、各車輪の操舵角度α_１，α_２，α_３，α_４と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を制御することができる。

・・・・式（Ｅ１１）

・・・・・式（２９）

・・・・・式（Ｅ１２）

・・・・・式（３０）

・・・・式（３１）
【００６４】
また操舵モードＭ３においては、次のように、点Pnの移動方向角度（操舵指令値）α_ｎを基に、各車輪の操舵角度α_１，α_２，α₃，α₄と回転速度ｎ_１，ｎ_２，ｎ_３，ｎ_４を制御することができる。

・・・・・式（３２）

・・・・・式（３３）

・・・・・式（Ｅ３３）

・・・・・式（３４）
【００６５】
【発明の効果】
上記実施例からも明らかなように、この発明に係る４輪独立操舵車両の操舵制御方法によれば、所定の操舵モードを形成する操舵拘束条件式の中の一つの変数を操舵指令値Ｓとし、その操舵指令値ＳをＳ_１からＳ_２へ変えて、各車輪の操舵角度α_１，α_２，α_３，α_４を、操舵指令値Ｓ_１に対応する各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から操舵指令値Ｓ_２に対応する各操舵角度［α_１，α_２，α_３，α_４］Ｓ_２ へ移行する過程で、操舵指令値Ｓ_１に微小操舵指令値ΔＳを加えた操舵指令値（Ｓ_１＋ΔＳ）に対して前記操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］Ｓ_１＋ΔＳ を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］Ｓ_１＋Δ_Ｓ に向けて各操舵角度α_１，α_２，α_３，α_４を変化させ、各操舵角度α_１，α_２，α_３，α_４が前記微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ΔＳ} に到達して舵角整合したことを検知しながら、微小操舵指令値ΔＳを順次加えた操舵指令値（Ｓ_１＋ｎΔＳ）に対して操舵拘束条件式を満たす微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ}を演算し、その微小移行操舵角度［α_１，α_２，α_３，α_４］_{Ｓ１＋ｎΔＳ} に向けて各操舵角度α_１，α_２，α_３，α_４を変化させて、各車輪の操舵角度α_１，α_２，α_３，α_４をそれぞれ操舵指令値Ｓ_１に対応する各操舵角度各操舵角度［α_１，α_２，α_３，α_４］_Ｓ１ から操舵指令値Ｓ_２に対応する各操舵角度各操舵角度［α_１，α_２，α_３，α_４］_Ｓ２ へ変化させることにより、車両の操舵過程で車輪の開閉脚現象が生ずることを防止することができる。
【００６６】
またこの発明によれば、例えば車両上に立つ運転者の位置など、車両上の任意の点Ｐｎの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_ｎや、あるいは左右の前車輪を結ぶ直線の中点Poの移動方向が車両の右車輪・左車輪間の中心線Ｙとなす角度α_０を操舵指令値として用いることにより、操舵指令値が運転者の操舵方向感覚に適合したものとなって、運転者の操舵操作の錯覚を防ぎ所望の方向への操舵を迅速正確に実行できるようになる。
【００６７】
またこの発明によれば、車両を停止状態から発信させる際、あるいは所定の操舵モードにおける操舵モード変更時に、各車輪の操舵角度α_１，α_２，α_３，α_４を一旦α_１＝α_２＝α_３＝α_４＝０の直進方向にリセットした後に、所定の操舵モードを形成する操舵拘束条件式に従って各操舵角度α_１，α_２，α_３，α_４を個別に変化させる。
【００６８】
またこの発明によれば、車両の発進時あるいは所定操舵モードの変更時に、各車輪の操舵角度α_１，α_２，α_３，α_４が、所定の操舵モードを形成する操舵拘束条件式を満たした後に、車両を走行駆動させることから、車両が停止状態から始動する際、あるいは操舵モードの変更時に、車両に衝撃を生ずることを防止して走行上の安全性を高め、車両を所定の操舵モードで所望に方向へ正しく円滑に始走行させることができる。
【図面の簡単な説明】
【図１】 この発明に係る電気移動車両の車体ベースの基本構成を示す平面図。
【図２】 同車体ベースに装着される車輪駆動・操舵ブロックの斜視図。
【図３】 操舵モードＭ１の説明図。
【図４】 操舵モードＭ２の説明図。
【図５】 操舵モードＭ３の説明図。
【図６】操舵モードＭ４の説明図。
【図７】操舵モードＭ５の説明図。
【図８】操舵モードＭ１における車両回転半径と操舵角度の関係図。
【図９】操舵モードＭ３における車両回転半径と操舵角度の関係図。
【図１０】操舵モードＭ１における操舵角度の車両回転半径に対する感度の関係図。
【図１１】操舵モードＭ３における操舵角度の車両回転半径に対する感度の関係図。
【図１２】操舵モードＭ１における車両回転半径と操舵角度の時間に対する関係図。
【図１３】操舵モードＭ１における操舵指令値と各車輪の操舵角度の関係図。
【図１４】操舵モードＭ３における操舵指令値と各車輪の操舵角度の関係図。
【符号の説明】
１ ：車体ベース
２１ ：右前車輪
２１ａ：右前車輪の駆動モータ ２１ｂ：右前車輪の操舵モータ
２２ ：左前車輪
２２ａ：左前車輪の駆動モータ ２２ｂ：左前車輪の操舵モータ
２３ ：左前車輪
２３ａ：右後車輪の駆動モータ ２３ｂ：右後車輪の操舵モータ
２４ ：左後車輪
２４ａ：左後車輪の駆動モータ ２４ｂ：左後車輪の駆動モータ
A1 ：右前車輪の走行向き B1 ：右前車輪の操舵・駆動ブロック
A2 ：左前車輪の走行向き B2 ：左前車輪の操舵・駆動ブロック
A3 ：右後車輪の走行向き B3 ：右後車輪の操舵・駆動ブロック
A4 ：左後車輪の走行向き B4 ：左後車輪の操舵・駆動ブロック
Ao ：左右の前車輪を結ぶ直線上の中点の移動方向
An ：車両上の任意の点の移動方向
ｄ ：点P5’，P6’の後車輪軸線H2からの距離
H1 ：前車輪軸線 H2 ：後車輪軸線
Ｌ ：点P1，P2，P3，P4の車両中心線Ｘからの距離
Ｍ１，Ｍ２，Ｍ３，Ｍ４，Ｍ５：操舵モード
N ：車両の前方直進方向
ｎ_１ ：右前車輪の回転速度
ｎ_２ ：左前車輪の回転速度
ｎ_３ ：右後車輪の回転速度
ｎ_４ ：左後車輪の回転速度
Ｏ ：各車輪位置P1，P2，P3，P4に対する中心点
P1 ：右前車輪の位置（点）
P2 ：左前車輪の位置（点）
P3 ：右後車輪の位置（点）
P3 ：左後車輪の位置（点）
P5 ：操舵モードＭ１における各車輪の右旋回同心円弧軌跡の中心点
P6 ：操舵モードＭ１における各車輪の左旋回同心円弧軌跡の中心点
P5’ ：操舵モードＭ３における右旋回の中心点
P6’ ：操舵モードＭ３における左旋回の中心点
Po ：左右の前車輪を結ぶ直線上の中点
Pn ：車両上の任意の点（Ｘ座標：x_n，Ｙ座標：y_n）
Ｒ ：操舵指令値（各車輪の旋回軌跡が同心円弧となる場合の同心円弧の中心点と各車輪の位置に対する中心点の間の距離）
Ｗ ：点P１，P２，Ｐ３，Ｐ４の車両中心線Ｙからの距離
Ｘ ：前車輪と後車輪の間の中心線（Ｘ軸）
Ｙ ：右車輪と左車輪の間の中心線（Y軸）
α_１ ：右前車輪の操舵角度
α_２ ：左前車輪の操舵角度
α_３ ：右後車輪の操舵角度
α_４ ：左後車輪の操舵角度
α_０ ：操舵指令値（左右の前車輪を結ぶ直線上の中点の移動方向が車両中心線Ｙとなす角度）
α_ｎ ：操舵指令値（車両上の任意の点の移動方向が車両中心線Ｙとなす角度）
ΔＲ，Δα_ｎ，Δα_０，：微小操舵指令値[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a steering control method for a vehicle (especially an electric mobile vehicle) that travels by four-wheel independent steering, and the vehicle is operated in a steering mode that adapts to the path configuration of a facility where the vehicle is traveling and the arrangement of objects around the path. The present invention relates to a vehicle steering control method for smoothly and safely traveling a vehicle. In the present invention, the “steering mode” means a basic pattern of a trajectory drawn by each wheel of a vehicle by steering.In the present invention, the “center point with respect to the position of each wheel” means a rectangular center point with the positions of the four wheels as apexes, that is, a point equidistant from the four wheel positions.
[0002]
[Prior art]
  In various indoor and outdoor facilities such as medical institutions, welfare facilities, logistics bases, computer storage buildings, large commercial facilities, libraries, sports / entertainment facilities, amusement parks, etc. In response to this, a method for running control of a four-wheel independent steering electric mobile vehicle in an appropriate steering mode has already been proposed in Japanese Patent Application No. 2001-351127.
[0003]
  That is, Japanese Patent Application No. 2001-351127 discloses an electric mobile vehicle in which left and right front wheels and left and right rear wheels are respectively steered and controlled by separate steering motors and drive motors. Steering modes M1, M2, M3, M4, and M5 are shown. As an example of the steering mode, the right rear wheel traveling locus and the left rear wheel traveling locus are respectively the right front wheel traveling locus and the left front wheel traveling. Steering mode M1 following the trajectory, Steering mode M2 in which the traveling trajectories of the front wheels and the rear wheels are parallel to each other, Steering mode M3 in which the trajectory of the rear wheels is a so-called inner wheel differential trajectory with respect to the turning trajectory of the front wheels, Steering mode M4 for turning the vehicle clockwise around the rear wheel or turning the vehicle counterclockwise around the left rear wheel, and turning the vehicle right around the right front wheel Steering mode M5 turning the vehicle counter-clockwise is shown around a is allowed or the front left wheel pivot Ri. Then, a steering mode suitable for the condition of the passage is selected from the steering modes M1, M2, M3, M4, and M5, and a steering constraint conditional expression (abbreviated as “condition” for the formation of the selected predetermined steering mode) is selected. The rotation of each steering motor and each drive motor is controlled according to the equation), and the steering angle α of each wheel is controlled.₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄There has been proposed a steering control method for controlling.
[0004]
  The following formulas have been proposed as steering constraint conditional formulas (conditional formulas) along the above-described steering modes.
For steering mode M1:

... Formula (E11)

... Formula (E12)

.... Formula (E13)
For steering mode M2:

... Formula (E21)

... Formula (E22)
For steering mode M3:

... Formula (E31)

... Formula (E32)

... Formula (E33)

... Formula (E34)
For steering mode M4:
When turning right,

... Formula (E41)

... Formula (E42)

... Formula (E43)

.... Formula (E44)
When turning left,

... Formula (E45)

... Formula (E46)

... Formula (E47)

... Formula (E48)
For steering mode M5:
When turning right,

... Formula (E51)

... Formula (E52)

... Formula (E53)

.... Formula (E54)
When turning left,

... Formula (E55)

... Formula (E56)

... Formula (E57)

... Formula (E58)
However, in the above conditional expression,
α₁Is the steering angle for the right front wheel.
α₂Is the steering angle for the left front wheel.
α₃Is the steering angle for the right rear wheel.
α₄Is the steering angle for the left rear wheel.
n₁Is the rotation speed for the right front wheel.
n₂Is the rotation speed for the left front wheel.
n₃Is the rotational speed for the right rear wheel.
n₄Is the rotational speed for the left rear wheel.
L is the distance between the center line X between the front wheel and the rear wheel and each wheel.
W is the distance between each wheel and the center line Y between the right and left wheels.
R is the distance between the center of the concentric arc and the center point with respect to the position of each wheel when the turning trajectory of each wheel is a concentric arc. (Distance from the center of the vehicle to the turning center of the vehicle, that is, the turning radius of the vehicle)
[0005]
  However, in order to change the traveling direction of the vehicle, the steering angle of each wheel according to the above conditional expression is obtained by increasing or decreasing the set value of the steering command value R using the distance (the turning radius of the vehicle) R as the steering command value. α₁, Α₂, Α₃, Α₄When the vehicle traveling direction is changed by decreasing or increasing the steering command value R, the steering command value R is changed to the current steering command value R.₁To the desired steering command value R₂Even if the setting is changed to₁, Α₂, Α₃, Α₄Since there is a slight time difference (steering command tracking time) until the vehicle reaches a new steering angle defined by the above conditional expression, in the steering process during the steering command tracking time, However, there is a possibility that an open leg phenomenon that causes the vehicle to spread in the traveling direction of the vehicle or a closed leg phenomenon in which the directions of the left and right wheels are in a sag state with respect to the traveling direction of the vehicle. In addition, the open leg phenomenon and the closed leg phenomenon are collectively referred to as an open / close leg phenomenon. If the open / close leg phenomenon occurs in the steering process, an excessive force is applied to the steering mechanism to cause a failure, and the stability of people and objects on the vehicle is impaired, which is dangerous.
[0006]
  In addition, it is difficult for a driver who actually rides and steers a vehicle to intuitively and physically sense the physical relationship between the wheel steering angle (vehicle traveling direction) and the distance R, and the distance R is In this case, the distance R changes discontinuously from −∞ to + ∞ or from + ∞ to −∞ on the left and right sides of the straight traveling direction of the vehicle.₁, Α₂, Α₃, Α₄It is not preferable to use it as a steering command value, that is, a steering angle setting parameter.
[0007]
[Patent Document 1]
Japanese Patent Application No. 2001-351127
[0008]
[Problems to be solved by the invention]
In view of the above-described steering problems, the present invention prevents a wheel opening / closing leg phenomenon from occurring in the steering process of a four-wheel independent steering vehicle, and at the same time, a distance R corresponding to the turning (turning) radius of the vehicle. By using a steering command value that makes it easier to understand the physical relationship between the steering command value and the vehicle traveling direction in light of the steering feeling of the driver operating the vehicle, It is intended to prevent the illusion of steering operation and to steer quickly and accurately in a desired direction. Also, when starting to run from when the vehicle is stopped or when changing the steering mode, it is intended to prevent the vehicle from being impacted and to prevent the vehicle from starting and running in an unintended direction. is there.
[0009]
[Means for Solving the Problems]
  In order to solve the above problems and achieve the object, the present invention uses the following various means.
[0010]
In order to prevent the opening / closing leg phenomenon of the wheels from occurring in the steering process of the four-wheel independent steering vehicle, the present invention is adapted to change the steering command value to change the four vehicle conditions according to the steering constraint condition formula that forms a predetermined steering mode. Wheel steering angle α₁, Α₂, Α₃, Α₄In the steering control that individually controls the vehicle and changes the traveling direction of the vehicle, one variable in the steering constraint condition formula is set as the steering command value S, and the steering command value S is set to S₁To S₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S1 To steering command value S₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S2 In the process of shifting to the steering command value S₁To the steering command value (S₁+ ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α_{4] S1 + ΔS} , The steering command value (S₁Steering command value (S) obtained by adding a small steering command value ΔS to + ΔS)₁+ 2ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄] S₁+ 2ΔS is calculated, and its small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the steering command value (S₁+ NΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_S1 To each steering angle [α₁, Α₂, Α₃, Α₄]_S2 The steering control of the four-wheel independent steering vehicle is performed by changing to
[0011]
  When the wheel drive motor is a synchronous motor or an induction motor, the steering angle α of each wheel₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄Steering control is performed by individually changing. That is, each steering angle α of each of the four wheels of the vehicle according to a steering constraint conditional expression that forms a predetermined steering mode by changing the steering command value.₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄In the steering control that individually controls the vehicle and changes the traveling direction of the vehicle, one variable in the steering constraint condition formula is set as the steering command value S, and the steering command value S is set to S₁To S₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S1 To steering command value S₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S2 In the process of shifting to the steering command value S₁To the steering command value (S₁+ ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} And minute transition rotation speed [n₁, N₂, N3, n4]_{S1 + ΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + ΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} , The steering command value (S₁Steering command value (S) obtained by adding a small steering command value ΔS to + ΔS)₁+ 2ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + 2ΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + 2ΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value obtained by sequentially adding a small steering command value ΔS after detecting that the steering angle is matched._{(S1 + nΔS)}The small transition steering angle [α satisfying the steering constraint condition formula₁, Α₂, Α₃, Α₄]_{S1 + nΔS}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + nΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + nΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_S1 To each steering angle [α₁, Α₂, Α₃, Α₄]_S2 The steering control of the four-wheel independent steering vehicle is performed by changing to
[0012]
  As an example of the steering command value actually used, the distance R between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel is used as the steering command value. That is, each steering angle α of each of the four wheels of the vehicle according to a steering constraint conditional expression that forms a predetermined steering mode by changing the steering command value.₁, Α₂, Α₃, Α₄In the steering control to change the traveling direction of the vehicle by individually controlling the vehicle, the steering command value is the distance R between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel. And the steering command value R is R₁To R₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value R₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_R1 To each steering angle [α corresponding to the steering command value R2₁, Α₂, Α₃, Α₄]_R2 In the process of shifting to the steering command value (R) obtained by adding a small steering command value ΔR to the steering command value R1.₁+ ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} , The steering command value (R₁Steering command value (R) obtained by adding a small steering command value ΔR to + ΔR)₁+ 2ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} Each steering angle α toward₁, Α₂, Α₃, Α₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the steering command value (R₁+ NΔR), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_R1 To each steering angle [α₁, Α₂, Α₃, Α₄]_R2 The steering control of the four-wheel independent steering vehicle is performed by changing to
[0013]
  When the wheel drive motor is a synchronous motor or an induction motor, the steering command value is the distance R between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel. The steering command value R is R₁To R₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value R₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_R1 To steering command value R₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_R2  In the process of shifting to the steering command value R₁To the steering command value (R₁+ ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + ΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + ΔR}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} , The steering command value (R₁Steering command value (R) obtained by adding a small steering command value ΔR to + ΔR)₁+ 2ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + 2ΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + 2ΔR}  Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After the steering alignment is detected, a steering command value (R₁+ NΔR), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + nΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + nΔR}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_R1 To each steering angle [α₁, Α₂, Α₃, Α₄]_R2 The steering control of the wheel independent steering vehicle is performed by changing to
[0014]
  In addition, as an example of a predetermined steering mode which is considered to be frequently used, a steering mode (abbreviated for the right rear wheel and the left front wheel follows the right front wheel and the left front wheel respectively) And a steering restraint condition that forms a steering mode for a steering mode (abbreviated as “steering mode M3” for short) in which the turning trajectory of the rear wheel is a so-called inner wheel difference trajectory with respect to the turning trajectory of the front wheel. Make the expression explicit.
[0015]
That is, when the steering command value is the distance R between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel, the right front wheel, the left front wheel, The steering angle for each of the left rear wheels is α₁, Α₂, Α₃, Α₄And the rotational speed for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is n.₁, N₂, N₃, N₄And the distance between the center line X between the front wheel and the rear wheel and each wheel is L, and the distance between the center line Y between the right wheel and the left wheel and each wheel is W,
The steering constraint conditional expression that forms the steering mode M1 is

And a conditional expression that can be expressed as
The steering restraint conditional expression that forms the steering mode M3 is

A conditional expression that can be expressed as
Note that the rotational speed n for each of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel in steering control₁, N₂, N₃, N₄If it is not necessary to forcibly control the₁: N₂: N₃: N₄The conditional expression for is unnecessary.
[0016]
  Further, the present invention provides the above steering command value so that the steering command value is adapted to the driver's sense of steering direction, and the illusion of the steering operation of the driver is prevented so that steering in a desired direction can be performed reliably. As a steering command value instead of the value R (distance R corresponding to the turning radius of the vehicle), an angle α formed by the moving direction of an arbitrary point Pn on the vehicle and the center line Y between the right wheel and the left wheel of the vehicle_n, Or the angle α between the moving direction of the midpoint Po of the straight line connecting the left and right front wheels and the center line Y between the right and left wheels of the vehicle₀Is used.
[0017]
  That is, according to the present invention, the steering angle α of each of the four wheels of the vehicle is changed according to the steering constraint conditional expression that forms a predetermined steering mode by changing the way of taking the steering command value.₁, Α₂, Α₃, Α₄In the steering control in which the traveling direction of the vehicle is changed by individually controlling the vehicle, the angle α between the moving direction of an arbitrary point Pn on the vehicle and the center line Y between the right wheel and the left wheel of the vehicle_nIs the steering command value, and the steering command value α_nΑ_n1To α_n2Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value α_n1Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_αn1 To steering command value α_n2Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_αn2 In the process of shifting to the steering command value α_n1A small steering command value Δα_nSteering command value (α_n1+ Δα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}And the steering command value (α_n1+ Δα_n) Further steering command value Δα_nSteering command value (α_n1+ 2Δα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + 2Δαn} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + 2Δαn} Each steering angle α toward₁, Α₂, Α₃, Α₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the small steering command value Δα_nSteering command value (α_n1+ NΔα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn}The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_αn1 To each steering angle [α₁, Α₂, Α₃, Α₄]_αn2 The steering control of the four-wheel independent steering vehicle is performed by changing to
[0018]
  Alternatively, the steering angle α of each of the four wheels of the vehicle is changed according to a steering constraint conditional expression that forms a predetermined steering mode by changing how to take the steering command value.₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄In the steering control in which the traveling direction of the vehicle is changed by individually controlling the vehicle, the angle α between the moving direction of an arbitrary point Pn on the vehicle and the center line Y between the right wheel and the left wheel of the vehicle_nIs the steering command value, and the steering command value α_nΑ_n1To α_n2Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value α_n1Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_αn1 To steering command value α_n2Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_αn2 In the process of shifting to the steering command value α_n1A small steering command value Δα_nSteering command value (α_n1+ Δα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn + Δαn}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn1 + Δαn}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + Δαn}And the steering command value (α_n1+ Δα_n) Further steering command value Δα_nSteering command value (α_n1+ 2Δα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + 2Δαn}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn1 + 2Δαn}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + 2Δαn} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn1 + 2Δαn}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the small steering command value Δα_nSteering command value (α_n1+ NΔα_n) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn1 + nΔαn}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn}And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{αn1 + nΔαn}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + nΔαn}The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_αn1 To each steering angle [α₁, Α₂, Α₃, Α₄]_αn2 The steering control of the four-wheel independent steering vehicle is performed by changing the position.
[0019]
  The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α₁, Α₂, Α₃, Α₄And the rotational speed for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is n.₁, N₂, N₃, N₄The distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and the distance between each wheel is W, and any on the vehicle X coordinate of the point Pn_n, Y coordinate is y_nAnd the angle between the movement direction of the point Pn and the center line Y between the right and left wheels of the vehicle is α_nAnd the angle α_nAs a steering command value, a steering constraint conditional expression for forming a predetermined steering mode M1 is

And a conditional expression that can be expressed as
The steering constraint conditional expression that forms the predetermined steering mode M3 is

A conditional expression that can be expressed as
Note that the rotational speed n for each of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel in steering control₁, N₂, N₃, N₄If it is not necessary to forcibly control the₁: N₂: N₃: N₄The conditional expression for is unnecessary.
[0020]
  In addition, the present invention changes each steering angle α of the four wheels of the vehicle in accordance with a steering constraint conditional expression that forms a predetermined steering mode by changing how to take the steering command value.₁, Α₂, Α₃, Α₄In the steering control that changes the traveling direction of the vehicle by individually controlling the vehicle, the angle α formed by the moving direction of the midpoint P0 of the straight line connecting the left and right front wheels with the center line Y between the right wheel and the left wheel of the vehicle₀Is the steering command value, and the steering command value α₀Α₀₁To α₀₂Change each steering angle α₁, Α₂, Α₃, Α₄Steering command value α₀₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_α01 To steering command value α₀₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_α02In the process of shifting to the steering command value α₀₁A small steering command value Δα₀Steering command value (α₀₁+ Δα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0}Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0} And the steering command value (α₀₁+ Δα₀) Further steering command value Δα₀Steering command value (α₀₁+ 2Δα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{αn1 + 2Δα0}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + 2Δα0}Each steering angle α toward₁, Α₂, Α₃, Α₄After that, similarly, each steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the small steering command value Δα₀Steering command value (α₀₁+ NΔα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0}Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0}The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_α01 To each steering angle [α₁, Α₂, Α₃, Α₄]_α02 The steering control of the four-wheel independent steering vehicle is performed by changing to.
[0021]
Alternatively, the steering angle α of each of the four wheels of the vehicle is changed according to a steering constraint conditional expression that forms a predetermined steering mode by changing how to take the steering command value.₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄In the steering control that changes the traveling direction of the vehicle by individually controlling the angle α, the angle α between the moving direction of the midpoint Po of the straight line connecting the left and right front wheels and the center line Y between the right wheel and the left wheel of the vehicle₀Is the steering command value, and the steering command value α₀Α₀₁To α₀₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value α₀₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_α01 To each steering command value α₀₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_α02 In the process of shifting to the steering command value α₀₁A small steering command value Δα₀Steering command value (α₀₁+ Δα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + Δα0}Is calculated, and the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + Δα0}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + Δα0} And the steering command value (α₀₁+ Δα₀) Further steering command value Δα₀Steering command value (α₀₁+ 2Δα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + 2Δα0} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + 2Δα0}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + 2Δα0} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + 2Δα0}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the small steering command value Δα₀Steering command value (α₀₁+ NΔα₀) With respect to the small steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + nΔα0}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{α01 + nΔα0}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{α01 + nΔα0}The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_α01 To each steering angle [α₁, Α₂, Α₃, Α₄]_α02 The steering control of the four-wheel independent steering vehicle is performed by changing to.
[0022]
  The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α₁, Α₂, Α₃, Α₄And the rotational speed for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is n.₁, N₂, N₃, N₄The distance between the center line X between the front wheel and the rear wheel and each wheel is L, the distance between the center line Y between the right wheel and the left wheel and each wheel is W, and the left and right front wheels The angle formed by the movement direction of the midpoint Po of the straight line connecting the vehicle and the center line Y between the right and left wheels of the vehicle is α₀And the angle α₀As a steering command value, a steering constraint conditional expression for forming a predetermined steering mode M1 is

And a conditional expression that can be expressed as
The steering constraint conditional expression that forms the predetermined steering mode M3 is

A conditional expression that can be expressed as
Note that the rotational speed n for each of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel in steering control₁, N₂, N₃, N₄If it is not necessary to forcibly control the₁: N₂: N₃: N₄The conditional expression for is unnecessary.
[0023]
  Further, the present invention enables a vehicle to start and run smoothly in a desired direction in a predetermined steering mode without causing an impact on the vehicle when the vehicle starts running from a stopped state or when the steering mode is changed. In addition, when changing the steering mode in a plurality of types of steering modes including forward / reverse modes of the vehicle, the steering angle α of each wheel₁, Α₂, Α₃, Α₄Once α₁= Α₂= Α₃= Α₄After resetting in the straight direction of = 0, each steering angle α according to the steering constraint condition formula that forms a predetermined steering mode₁, Α₂, Α₃, Α₄Vary individually.
[0024]
  In addition, when changing a predetermined steering mode arbitrarily selected from a plurality of types of steering modes including forward / reverse modes of the vehicle, the steering angle α of each wheel₁, Α₂, Α₃, Α₄However, after satisfying the steering constraint condition formula after the change of the steering mode, the vehicle is driven to travel.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
One of the basic embodiments of the present invention is that each steering angle α of each of the four wheels of the vehicle is changed according to a steering constraint conditional expression that forms a predetermined steering mode by changing a steering command value.₁, Α₂, Α₃, Α₄In the steering control that individually controls the vehicle and changes the traveling direction of the vehicle, one variable in the steering constraint condition formula is set as the steering command value S, and the steering command value S is set to S₁To S₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄] S₁ To each steering angle [α corresponding to the steering command value S2₁, Α₂, Α₃, Α₄]_S2 In the process of shifting to the steering command value S₁To the steering command value (S₁+ ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} , The steering command value (S₁Steering command value (S) obtained by adding a small steering command value ΔS to + ΔS)₁+ 2ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the steering command value (S₁+ NΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_S1 To each steering angle [α₁, Α₂, Α₃, Α₄]_S2 This is a steering control method for a four-wheel independent steering vehicle to be changed to
[0026]
  Further, in another basic embodiment of the present invention, the steering angle α of each of the four wheels of the vehicle is changed in accordance with a steering constraint conditional expression that forms a predetermined steering mode by changing the way of taking the steering command value.₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄In the steering control that individually controls the vehicle and changes the traveling direction of the vehicle, one variable in the steering constraint condition formula is set as the steering command value S, and the steering command value S is set to S₁To S₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S1 To steering command value S₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄] S₂ In the process of shifting to the steering command value S₁To the steering command value (S₁+ ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + ΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + ΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} , The steering command value (S₁Steering command value (S) obtained by adding a small steering command value ΔS to + ΔS)₁+ 2ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{S2 + 2ΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + 2ΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + 2ΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After detecting that the steering angle is matched, the steering command value (S₁+ NΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + nΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{S1 + nΔS}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} The steering angle α1, α2, α3, α4 of each wheel is changed to each steering angle [α₁, Α₂, Α₃, Α₄]_S1 To each steering angle [α₁, Α₂, Α₃, Α₄]_S2 This is a steering control method for a four-wheel independent steering vehicle to be changed to
[0027]
【Example】
  The present invention will be described below with reference to the drawings showing its embodiments. FIG. 1 is a plan view showing a basic structure of a vehicle body base of an electric mobile vehicle according to the present invention, and FIG. 2 is a perspective view of a wheel steering / drive block mounted on the vehicle body base. In FIG. 1, 1 is a vehicle body base of an electric mobile vehicle, points P1 and P2 indicate the positions of two left and right front wheels mounted on the lower surface of the vehicle body base 1, and points P3 and P4 are mounted on the lower surface of the vehicle body base 1. It shows the position of the two left and right rear wheels. Further, 21 indicates a right front wheel, 22 indicates a left front wheel, 23 indicates a right rear wheel, 24 indicates a left rear wheel, and an arrow N indicates a straight forward direction of the vehicle. The positions of the points P1, P2, P3, P4 (the positions of the wheels 21, 22, 23, 24) are at the positions of the vertices of the rectangle, and O is the center point of the rectangle, that is, the points P1, P2, P3. This is the center point for P4.In other words, as is clear from FIGS. 1 and 3, the center point O with respect to the positions P1, P2, P3, and P4 of the respective wheels has apexes at the positions P1, P2, P3, and P4 of the four wheels. It means a rectangular center point, that is, a point equidistant from each of the four wheel positions.The X axis and the Y axis are orthogonal coordinate axes passing through the center point O and are virtually set to explain the present invention. The X axis is the center line between the front wheels 21 and 22 and the rear wheels 23 and 24 (the center line in the left-right direction of the vehicle), and the Y axis is the center between the right wheels 21 and 23 and the left wheels 22 and 24. It is a line (center line in the longitudinal direction of the vehicle). The direction of the Y-axis is the same as the forward straight direction of the vehicle indicated by the arrow N, H1 is the front wheel axis connecting the points P1 and P2, and corresponds to the virtual axle of the front wheels 21 and 22, and H2 is the point P3. The rear wheel axis connecting P4 corresponds to the virtual axles of the rear wheels 23 and 24. L is the distance from the X axis to each point P1, P2, P3, P4, and W is the distance from the Y axis to each point P1, P2, P3, P4. P0 represents the midpoint of a straight line connecting the position P1 of the right front wheel and the position P2 of the left front wheel. Furthermore, Pn is an arbitrary point on the vehicle body base 1, for example, a position where the driver of the vehicle stands. The position of the point Pn is a coordinate (X coordinate: xn, Y coordinate: yn) with respect to the orthogonal coordinate axes X, Y. It is shown. A0 indicates the moving direction of the point P0 as the vehicle travels, and α0 indicates the angle (the moving direction angle of the midpoint P0 accompanying steering) that the moving direction A0 of the point P0 makes with the center line Y of the vehicle. An indicates the moving direction of the point Pn as the vehicle travels, and αn indicates the angle that the moving direction An of the point Pn makes with the center line Y of the vehicle (the moving direction angle of the point Pn due to steering).
[0028]
n₁, N₂, N₃, N₄Are the rotational speeds of the right front wheel 21, the left front wheel 22, the right rear wheel 23, and the left rear wheel 24, respectively.₁, Α₂, Α₃, Α₄These represent the steering angles of the right front wheel 21, the left front wheel 22, the right rear wheel 23, and the left rear wheel 24, respectively, during the steering control of the vehicle. A1, A2, A3, and A4 represent the directions (traveling directions) of the right front wheel 21, the left front wheel 22, the right rear wheel 23, and the left rear wheel 24, respectively, during the steering control of the vehicle.
[0029]
Rotational speed n of each wheel 21, 22, 23, 24 at the time of vehicle steering control₁, N₂, N₃, N₄And its steering angle α₁, Α₂, Α₃, Α₄Are individually controlled independently. For this reason, as shown in FIG. 2, drive motors 21a, 22a, 23a, 24a for rotational speed control are respectively provided on the front wheels 21, 22 and the rear wheels 23, 24. Steering motors 21b, 22b, 23b, 24b for steering angle control are connected to form individual steering / drive blocks B1, B2, B3, B4. Further, the actual traveling direction (actual steering angle) of each of the wheels 21, 22, 23, and 24 during vehicle traveling control is detected by a steering angle sensor, and the detection signal is fed back to the control system so that the driver can Steering angle α corresponding to the set steering command value₁, Α₂, Α₃, Α₄Street steering control is maintained. In addition, steering modes M1, M2, M3, M4, and M5 are prepared for the above-described vehicle, and a calculation program for calculating the steering angle and rotational speed of each wheel necessary to form each steering mode. The calculation means (computer) provided with is incorporated in the electric mobile vehicle. Note that a DC motor, a synchronous motor, an induction motor 4 or the like is used as a wheel drive motor. However, when a DC motor of the same specification is adopted for four drive motors and these are connected in series, four motors are used. As long as there is no idling of the wheel due to the electric circuit complementary action of the drive motor, the rotational speed n₁, N₂, N₃, N₃, N₄This ratio automatically satisfies the constraint equation, so there is no need to control the drive motors independently.
[0030]
  As shown in FIG. 3, the steering mode M1 is a steering angle α of the front wheels.₁, Α₂And rear wheel steering angle α₃, Α₄Is a steering mode in which the trajectories of the left and right rear wheels follow the trajectories of the left and right front wheels, respectively. In FIG. 3, point P5 (X coordinate: R, Y coordinate: 0) indicates the center point when the vehicle turns clockwise (clockwise turn) (CW), and point P6 (X coordinate: -R, Y coordinate: 0) indicates a center point when the vehicle turns counterclockwise (counterclockwise) (CCW). In the steering mode M1, as shown in FIG. 3, the turning trajectory of each wheel is a concentric arc, but the points P5 and P6 are also the centers of the concentric arc. As is clear from FIG. 3, in order to travel in the steering mode M1, the steering angle α₁, Α₂Is the steering angle α of each wheel 21, 22, 23, 24 under the conditions shown in Table 1 below.₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄The following steering constraint conditional expressions (conditional expressions) (E11), (E12), and (E13) must be satisfied and maintained.
[0031]
[Table 1]

[0032]

... Formula (E11)

... Formula (E12)

..... Formula (E13)
[0033]
As shown in FIG. 4, the steering mode M2 is a steering angle α of the front wheels.₁, Α₂And rear wheel steering angle α₃, Α₄This is a steering mode in which the vehicle is moved in parallel in the left-right and diagonal directions with the front and rear wheels all in a parallel pattern by cutting both the same direction and the same angle. As apparent from FIG. 4, in order to travel in the steering mode M2, the steering angle α of each wheel₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄The following conditional expressions (E21) and (E22) must be satisfied and maintained.
[0034]

... Formula (E21)

... Formula (E22)
[0035]
As shown in FIG. 5, the steering mode M3 is a steering angle α of the front wheels.₁, Α₂In the same steering mode as a conventional automobile that only steers the vehicle, the trajectory between the front wheels and the rear wheels is a steering mode that draws a so-called inner wheel difference trajectory. As apparent from FIG. 5, in the steering mode M3, the steering angle α of each wheel₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄The following conditional expressions (E31), (E32), (E33), and (E34) are satisfied and maintained. As shown in FIG. 5, the point P5 ′ serving as the center of the right turn and the point P6 ′ serving as the center of the left turn in the steering mode M3 are respectively separated from the rear wheel axis H2 by a distance d. When the vehicle speed is low, it can be considered that d≈0.
[0036]

... Formula (E31)

... Formula (E32)

.... Formula (E33)

.... Formula (E34)
However,

Since the vehicle travels at a low speed, d = 0 is set.
[0037]
In the steering mode M4, as shown in FIG. 6, the vehicle turns clockwise (clockwise) (CW) around the right rear wheel (point P3), or the vehicle turns around the left rear wheel (point P4). This is a steering mode for turning counterclockwise (counterclockwise) (CCW). As apparent from FIG. 6, in traveling in the steering mode M4, the steering angle α of each wheel is₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄The following conditional expressions (E41), (E42), (E43), (E44), (E45), (E46), (E47), and (E48) must be satisfied and maintained.
[0038]
That is, when turning the vehicle in the clockwise direction (CW) with the right rear wheel (point P3) as the center of rotation,

... Formula (E41)

... Formula (E42)

... Formula (E43)

... Formula (E44)
However,

[0039]
  That is, when turning the vehicle counterclockwise (CCW) with the left rear wheel (point P4) as the center of rotation,

.... Formula (E45)

... Formula (E46)

... Formula (E47)

... Formula (E48)
However,

[0040]
As shown in FIG. 7, the steering mode M5 turns the vehicle clockwise (clockwise) (CW) around the right front wheel (point P1) or turns the vehicle counterclockwise (counterclockwise) around the left front wheel (point P2). This is a steering mode for turning clockwise (CCW). As is apparent from FIG. 7, in the traveling in the steering mode M5, the steering angle α of each wheel is₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄The following conditional expressions (E51), (E52), (E53), (E54), (E55), (E56), (E57), and (E58) must be maintained.
[0041]
That is, when turning the vehicle clockwise (CW) with the front right wheel (point P1) as the center of rotation,

... Formula (E51)

・ ・ ・ ・ ・ Formula (E52)

... Formula (E53)

... Formula (E54)
However,

[0042]
That is, when turning the vehicle counterclockwise (CCW) with the left front wheel (point P2) as the center of rotation,

... Formula (E55)

.... Formula (E56)

... Formula (E57)

... Formula (E58)
However,

[0043]
  Thus, since the trajectory followed by each of the four wheels in the respective steering modes M1, M2, M3, M4, and M5 is not the same, the wheel must be driven at a rotational speed that matches the arc length of each trajectory. Steering angle α of each wheel 21, 22, 23, 24₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄Must be controlled to satisfy the conditions of the conditional expressions (E11) to (E58) determined by the vehicle speed and direction commands and the steering mode both during and after the steering transition. . If this condition is not satisfied, the wheel slips or slips, or an open / close leg phenomenon occurs between the left and right wheels.
[0044]
  Therefore, the vehicle has the steering angle α of each wheel based on the steering constraint conditional expressions (E11) and (E12) necessary for steering along the steering mode M1.₁, Α₂, Α₃, Α₄ The steering angle α of each wheel is calculated based on a calculation constraint calculation formula (E21) necessary for steering along the steering mode M2.₁, Α₂, Α₃, Α₄ And the steering angle α of each wheel based on the steering constraint conditional expressions (E31), (E32), and (E33) necessary for steering along the steering mode M3.₁, Α₂, Α₃, Α₄ Steering angle of each wheel based on a calculation program for calculating the steering constraint conditional expressions (E41), (E42), (E43), (E45), (E46), and (E47) necessary for steering along the steering mode M4 α₁, Α₂, Α₃, Α₄ Steering angle of each wheel based on the calculation program for calculating the steering restraint conditional expressions (E51), (E52), (E53), (E55), (E56), and (E57) necessary for steering along the steering mode M5 Wheel steering angle calculation means storing a calculation program for calculating α1, α2, α3, α4 is installed.
[0045]
Further, the vehicle has a rotational speed n of each wheel based on the steering constraint conditional expression (E13) necessary for steering along the steering mode M1.₁, N₂, N₃, N₄ , The rotational speed n of each wheel based on the steering constraint conditional expression (E22) required for steering along the steering mode M2.₁, N₂, N₃, N₄ , The rotational speed n of each wheel based on the steering restraint conditional expression (E34) necessary for steering along the steering mode M3.₁, N₂, N₃, N₄ Based on the steering constraint conditional expressions (E44) and (E48) necessary for steering along the steering mode M4, and the rotational speed n of each wheel.₁, N₂, N₃, N₄ Based on the steering constraint conditional expressions (E54) and (E58) necessary for steering along the steering mode M5, and the rotational speed n of each wheel.₁, N₂, N₃, N₄ Wheel rotation speed calculation means in which a calculation program for calculating is stored is installed.
[0046]
  The present invention is designed to prevent the opening / closing leg phenomenon of the wheels by controlling so as to always satisfy the above-described steering restraint conditional expression while the vehicle is running, that is, in the steering process of the four-wheel independent steering vehicle. Wheel steering angle α₁, Α₂, Α₃, Α₄It is necessary to consider the “steering command value” for setting and changing.
[0047]
For example, in the steering mode M1, as described above, the steering angle α₁, Α₂, Α₃, Α₄Is defined by the equations (E11) and (E12).

... Formula (E11)

.... Formula (E12)
Where the variable is α₁, Α₂, Α₃, Α₄Since there are four formulas with 5 and R, if one of the variables is determined, the other four variables are uniquely determined. Since the distance L and the distance W are determined by the vehicle design, the steering angle α is determined by determining the distance R.₁, Α₂, Α₃, Α₄Is uniquely determined. Accordingly, the distance (the turning radius of the vehicle) R has been used as the “steering command value”.
[0048]
Further, for example, in the steering mode M3, as described above, the steering angle α₁, Α₂, Α₃, Α₄Is defined by the equations (E31), (E32), and (E33).

... Formula (E31)

... Formula (E32)

.... Formula (E33)
Where the variable is α₁, Α₂Since there are two formulas with 3 and R, if one of the variables is determined, the other two variables are uniquely determined. Since the distance L and the distance W are determined by the vehicle design, the steering angle α is determined by determining the distance R.₁, Α₂, Α₃, Α₄Is uniquely determined. Accordingly, the distance (the turning radius of the vehicle) R has been used as the “steering command value”.
[0049]
  Here, W = 0.5m, L = 1m, distance R and steering angle α₁, Α₂, Α₃, Α₄Is obtained in the steering mode M1, and the characteristic shown in FIG. 9 is obtained in the steering mode M3. Next, taking the steering mode M1 as an example, the steering angle α when steering from R = 1 m to R = 2 m₁, Α₂When the change of the steering angle α is examined from FIG.₁Changes from 63.2 degrees to 33.7 degrees, and the range of change is 63.2-33.7 = 29.5 degrees, the steering angle α₂It can be seen that changes from 33.7 degrees to 21.8 degrees and the range of change is 33.7-21.8 = 11.9 degrees. Therefore, the steering angle α₁And steering angle α₂Are rotated at the same angular velocity, the steering angle α₂When the target value is reached, the steering angle α₁Is still in the middle of rotation toward the target value, and the left and right wheels are in a state of spreading forward with respect to the traveling direction, and a leg opening phenomenon occurs. Further, when steering from R = 1 m to R = 2 m, the opposite leg closing phenomenon occurs. When the open / close leg phenomenon occurs, not only the steering mechanism is forced, but also the person riding in the vehicle must turn forward and be dangerous, so the open / close leg phenomenon must be prevented. In order to prevent the open / close leg phenomenon, it is understood that the conditional expressions (E11) and (E12) must be satisfied in all time sections in which the vehicle is moving. The same applies to the steering modes M2, M3, M4, and M5 as well as the steering mode M1. In this application, that the steering angle of each wheel of the vehicle (the traveling direction of each wheel) becomes an angle that satisfies each steering constraint condition expression is referred to as “steering angle matching” in the present application.
[0050]
  One method for realizing the steering angle matching is that the driver changes the distance R, which is the steering command value, and sets a new steering command value (distance) to change the steering angle α.₁, Α₂, Α₃, Α₄When the steering command value (distance) R is gradually changed, the steering angle satisfying the steering constraint condition formula is calculated at each time to obtain the steering angle α₁, Α₂, Α₃, Α₄After a slight steering command follow time, the steering command value (distance) R is led to the newly set steering command value (changed steering command target value) and the steering angle α₁, Α₂, Α₃, Α₄Is shifted to the intended steering angle corresponding to the newly set steering command value.
[0051]
That is, by changing the steering command value, each steering angle α of each of the four wheels of the vehicle according to a steering constraint condition formula that forms a predetermined steering mode.₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄In the steering control to change the traveling direction of the vehicle by individually controlling the vehicle, the steering command value is the distance R between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel. And the steering command value R is R₁To R₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value R₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_R1 To steering command value R₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_R2  In the process of shifting to the steering command value R₁To the steering command value (R₁+ ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + ΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + ΔR}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + ΔR} , The steering command value (R₁Steering command value (R) obtained by adding a small steering command value ΔR to + ΔR)₁+ 2ΔR), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + 2ΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + 2ΔR} And its minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + 2ΔR}  Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Thereafter, similarly, the steering angle α of each wheel₁, Α₂, Α₃, Α₄After the steering alignment is detected, a steering command value (R₁+ NΔR), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR}And minute transition rotation speed [n₁, N₂, N₃, N₄]_{R1 + nΔR}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} And its minute transition rotation speed [n1, n2, n3, n4]_{R1 + nΔR}Each steering angle α toward₁, Α₂, Α₃, Α₄And each rotation speed n₁, N₂, N₃, N₄Each steering angle α₁, Α₂, Α₃, Α₄Is the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{R1 + nΔR} The steering angle α of each wheel is₁, Α₂, Α₃, Α₄For each steering angle [α₁, Α₂, Α₃, Α₄]_R1 To each steering angle [α₁, Α₂, Α₃, Α₄]_R2 This steering control method is a feature of the present invention.
[0052]
  Next, for the steering mode M1, the sensitivity of the steering angle α of the wheel with respect to the distance (vehicle turning radius) (steering command value) R is examined. Since there are generally the following formulas (1) and (2), the conditional expression (E11) can be expanded as follows.

When,

・ ・ ・ ・ Official (1)

When,

...... Official (2)

.... Formula (E11)

・ ・ ・ ・ ・ Formula (1)
As well

・ ・ ・ ・ ・ Formula (2)
Here, FIG. 10 shows the calculation results obtained by adding W = 0.5 m and L = 1 m to the expressions (1) and (2). As is apparent from FIG. 10, in the region where R is small, the sensitivity of α to R is high, and the sensitivity differs depending on the left and right wheels. FIG. 11 shows the result of the same calculation for the steering mode M3. Similarly, it can be seen that α has a high sensitivity to R in a region where R is small, and the sensitivity differs depending on the left and right wheels.
[0053]
  Thus, the sensitivity of the wheel steering angle α to the distance (vehicle turning radius, that is, the steering command value) R varies greatly depending on the value of R. Therefore, the distance (vehicle turning radius) R is directly used as the steering command value. It is not appropriate to do. Therefore, it is conceivable to introduce a new function of distance R and time t, R = f (t), and to control the steering angle α of the wheel via the function R = f (t). The function introduction process in this case is as follows.
[0054]
  Equation (1) is modified as follows.

・ ・ ・ ・ ・ Formula (3)
As well

・ ・ ・ ・ ・ Formula (4)
here

(However, K = constant value)

.... Formula (5)
Therefore,

.... Formula (6)

.... Formula (7)
It becomes. If the following formula (3) is applied here, the formula (13) is reached. That is,

...... Official (3)

.... Formula (8)

.... Formula (9)

.... Formula (10)

..... Formula (11)
Here, if R = 0, W = 0.5, L = 1, and t = 0, the integral constant CL is CL = 0.463648 (rad). Therefore, if K = −π / 20,

..... Formula (12)

.... Formula (13)
That is, the distance R may be changed as a function of the time t shown in Expression (13). At this time, the steering angle α of the right front wheel₁, Steering angle α of front left wheel₂Are as shown in the following equations (14), (15), and (16), respectively.

... Formula (E11)

..... Formula (14)

... Formula (E12)

..... Formula (15)

.... Formula (16)
[0055]
  FIG. 12 shows the distance R with respect to time t and the steering angle α of the right front wheel.₁, Steering angle α of front left wheel₂It can be seen that the steering angle α of the right front wheel changes linearly with respect to time t. In this way, when the distance R from the center line Y in the front-rear direction of the vehicle to the rotation center of the vehicle is used as the steering command value, dα / dR changes greatly in the change region of R, so this is made constant. Introducing a new function R = f (t) for time t and distance R (for example, R = W + Ltan (−Kt + CL) in the case of the steering mode M1) and controlling the distance R as a function of time t Then, good control can be realized by controlling the steering angle α from the distance R.
[0056]
  As described above, when the distance R is used as the steering command value, the theoretical development becomes simple. However, when the driver actually performs steering control, it cannot be denied that the steering operation is difficult for the driver. That is, when the distance R is small and large, the sensitivity dα / dR is more than two orders of magnitude, the sensitivity dα / dR is oversensitive in the steering angle range in the vicinity of the straight traveling direction that is frequently used in actual driving, and the distance R is Since it reverses discontinuously from + ∞ to −∞ and from −∞ to + ∞, and since the distance R is the distance to the center of rotation of the vehicle in the lateral direction, it is difficult for the driver to be connected to the actual driving feeling. This makes the driver's steering operation difficult.
[0057]
  Therefore, in the present invention, the angle α formed by the moving direction of the midpoint P0 on the straight line connecting the left and right front wheels with the center line of the vehicle₀Is a steering command value instead of the distance R.
[0058]
That is, for example, in the steering mode M1 (see FIG. 3),

.... Formula (17)

.... Formula (18)
If the equation (18) is substituted into the above equations (E11), (E12), (E13), the steering angle α of each wheel₁, Α₂, Α₃, Α₄, And the rotational speed n of each wheel₁, N₂, N₃, N₄The ratio is as follows:

... Formula (19)

.... Formula (20)

..... Formula (21)
[0059]
  In the steering mode M3 (see FIG. 5),

.... Formula (22)

.... Formula (23)
If formula (23) is substituted into formulas (E31), (E32), and (E34), the steering angle α of each wheel₁, Α₂And the rotational speed n of each wheel₁, N₂, N₃, N₄The ratio is as follows:

... Formula (24)

.... Formula (25)

.... Formula (26)
[0060]
  Further, assuming that W = 0.5 m and L = 1 m, an angle α formed by the movement direction of the midpoint P0 with the vehicle center line Y₀And the steering angles α1, α2, α3, and α4 of the wheels are as shown in FIG. 13 in the steering mode M1 and as shown in FIG. 14 in the steering mode M3. Thus, as the steering command value of the steering control, the angle α formed by the moving direction of the midpoint P0 on the straight line connecting the left and right front wheels with the vehicle center line Y₀Compared with the case where the distance R is used as a steering command value, the control of the steering system in accordance with the sense of the vehicle traveling direction in the actual driving of the driver is eliminated. It can be performed.
[0061]
  Furthermore, instead of the midpoint P0, an arbitrary point Pn on the vehicle (X coordinate: x_n, Y coordinate: y_n) Is the angle α between the moving direction and the vehicle center line Y_nCan also be used as a steering command value. (See Figs. 3 and 5)
[0062]
Any point Pn on the vehicle (X coordinate: x_n, Y coordinate: y_n) Is the angle α between the moving direction and the vehicle center line Y_nIs the steering command value, the angle α_nAnd point Pn coordinates (x_n, Y_n) Have the following relationship:

... Formula (27)

... Formula (28)
[0063]
  In the steering mode M1, the following expressions (29), (30), and (31) are derived by substituting the above expression (28) into the above expressions (E11), (E12), and (E13). , Angle of movement of point Pn (steering command value) α_nBased on the steering angle α of each wheel₁, Α₂, Α₃, Α₄And rotation speed n₁, N₂, N₃, N₄Can be controlled.

.... Formula (E11)

... Formula (29)

... Formula (E12)

... Formula (30)

.... Formula (31)
[0064]
  In the steering mode M3, the movement direction angle (steering command value) α of the point Pn is as follows._nBased on the steering angle α of each wheel₁, Α₂, Α_Three, Α_FourAnd rotation speed n₁, N₂, N₃, N₄Can be controlled.

... Formula (32)

... Formula (33)

... Formula (E33)

... Formula (34)
[0065]
【The invention's effect】
  As apparent from the above embodiment, according to the steering control method for a four-wheel independent steering vehicle according to the present invention, one variable in the steering constraint conditional expression forming the predetermined steering mode is set as the steering command value S. The steering command value S is set to S₁To S₂Change the steering angle α of each wheel₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄]_S1 To steering command value S₂Each steering angle corresponding to [α₁, Α₂, Α₃, Α₄] S₂ In the process of shifting to the steering command value S₁To the steering command value (S₁+ ΔS), a small transition steering angle satisfying the steering constraint condition formula [α₁, Α₂, Α₃, Α₄] S₁+ ΔS is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄] S₁+ Δ_S Each steering angle α toward₁, Α₂, Α₃, Α₄Each steering angle α₁, Α₂, Α₃, Α₄Is the minute transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + ΔS} The steering command value (S₁+ NΔS), a small transition steering angle that satisfies the steering constraint condition formula [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS}Is calculated, and the small transition steering angle [α₁, Α₂, Α₃, Α₄]_{S1 + nΔS} Each steering angle α toward₁, Α₂, Α₃, Α₄To change the steering angle α of each wheel.₁, Α₂, Α₃, Α₄Steering command value S₁Each steering angle corresponding to each steering angle [α₁, Α₂, Α₃, Α₄]_S1 To steering command value S₂Each steering angle corresponding to each steering angle [α₁, Α₂, Α₃, Α₄]_S2 Thus, it is possible to prevent the opening / closing leg phenomenon of the wheels from occurring during the steering process of the vehicle.
[0066]
  Further, according to the present invention, for example, the angle α formed by the movement direction of an arbitrary point Pn on the vehicle, such as the position of the driver standing on the vehicle, with the center line Y between the right wheel and the left wheel of the vehicle._nOr the angle α between the moving direction of the midpoint Po of the straight line connecting the left and right front wheels and the center line Y between the right and left wheels of the vehicle₀Is used as a steering command value so that the steering command value is adapted to the driver's sense of steering direction, so that the driver's illusion of steering operation can be prevented and steering in a desired direction can be executed quickly and accurately. Become.
[0067]
  Further, according to the present invention, the steering angle α of each wheel when the vehicle is transmitted from a stopped state or when the steering mode is changed in a predetermined steering mode.₁, Α₂, Α₃, Α₄Once α₁= Α₂= Α₃= Α₄After resetting in the straight direction of = 0, each steering angle α according to the steering constraint condition formula that forms a predetermined steering mode₁, Α₂, Α₃, Α₄Vary individually.
[0068]
  Further, according to the present invention, the steering angle α of each wheel when the vehicle starts or when the predetermined steering mode is changed.₁, Α₂, Α₃, Α₄However, since the vehicle is driven after satisfying the steering constraint condition formula that forms the predetermined steering mode, it is possible to prevent the vehicle from being shocked when the vehicle is started from a stopped state or when the steering mode is changed. Thus, it is possible to improve safety in traveling and to start the vehicle correctly and smoothly in a desired direction in a predetermined steering mode.
[Brief description of the drawings]
FIG. 1 is a plan view showing a basic configuration of a vehicle body base of an electric mobile vehicle according to the present invention.
FIG. 2 is a perspective view of a wheel drive / steering block mounted on the vehicle body base.
FIG. 3 is an explanatory diagram of a steering mode M1.
FIG. 4 is an explanatory diagram of a steering mode M2.
FIG. 5 is an explanatory diagram of a steering mode M3.
FIG. 6 is an explanatory diagram of a steering mode M4.
FIG. 7 is an explanatory diagram of a steering mode M5.
FIG. 8 is a relationship diagram between a vehicle turning radius and a steering angle in a steering mode M1.
FIG. 9 is a relationship diagram between a vehicle turning radius and a steering angle in a steering mode M3.
FIG. 10 is a relationship diagram of the sensitivity of the steering angle to the vehicle turning radius in the steering mode M1.
FIG. 11 is a relationship diagram of the sensitivity of the steering angle to the vehicle turning radius in the steering mode M3.
FIG. 12 is a relationship diagram of vehicle turning radius and steering angle with respect to time in a steering mode M1.
FIG. 13 is a relationship diagram between a steering command value and a steering angle of each wheel in a steering mode M1.
FIG. 14 is a relationship diagram between a steering command value and a steering angle of each wheel in a steering mode M3.
[Explanation of symbols]
1: Body base
21: Front right wheel
21a: Driving motor for right front wheel 21b: Steering motor for right front wheel
22: Left front wheel
22a: Driving motor for left front wheel 22b: Steering motor for left front wheel
23: Front left wheel
23a: Driving motor for right rear wheel 23b: Steering motor for right rear wheel
24: Left rear wheel
24a: Drive motor for left rear wheel 24b: Drive motor for left rear wheel
A1: Driving direction of right front wheel B1: Steering / driving block of right front wheel
A2: Driving direction of left front wheel B2: Steering / drive block of left front wheel
A3: Driving direction of right rear wheel B3: Steering / drive block of right rear wheel
A4: Left rear wheel travel direction B4: Left rear wheel steering / drive block
Ao: Direction of movement of the midpoint on the straight line connecting the left and right front wheels
An: Direction of movement of any point on the vehicle
d: Distance from point P5 ', P6' to rear wheel axis H2
H1: Front wheel axis H2: Rear wheel axis
L: Distance from points P1, P2, P3, P4 to vehicle center line X
M1, M2, M3, M4, M5: Steering mode
N: Straight ahead direction of the vehicle
n₁   : Rotation speed of front right wheel
n₂   : Rotational speed of front left wheel
n₃  : Right rear wheel rotation speed
n₄  : Rotation speed of left rear wheel
O: Center point for each wheel position P1, P2, P3, P4
P1: Front right wheel position (point)
P2: Left front wheel position (point)
P3: Right rear wheel position (point)
P3: Left rear wheel position (point)
P5: Center point of the right-turning concentric circular arc trajectory of each wheel in the steering mode M1
P6: Center point of left-turning concentric arc trajectory of each wheel in steering mode M1
P5 ′: Center point of right turn in steering mode M3
P6 ': Center point of left turn in steering mode M3
Po: Midpoint on the straight line connecting the left and right front wheels
Pn: Any point on the vehicle (X coordinate: x_n, Y coordinate: y_n)
R: Steering command value (distance between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel)
W: Distance from points P1, P2, P3, P4 to vehicle center line Y
X: Center line between the front and rear wheels (X axis)
Y: Center line between right and left wheels (Y axis)
α₁ : Steering angle of right front wheel
α₂ : Steering angle of front left wheel
α₃ : Steering angle of right rear wheel
α₄ : Steering angle of left rear wheel
α₀ : Steering command value (An angle formed by the moving direction of the midpoint on the straight line connecting the left and right front wheels with the vehicle center line Y)
α_n : Steering command value (angle formed by the movement direction of an arbitrary point on the vehicle and the vehicle center line Y)
ΔR, Δα_n, Δα₀,: Micro steering command value

Claims (23)

By changing the method of obtaining the steering command value, the vehicle is controlled by individually controlling the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the four wheels of the vehicle in accordance with a steering constraint conditional expression that forms a predetermined steering mode. In the steering control for changing the traveling direction of the vehicle, one variable in the steering constraint condition formula is set as the steering command value S, and the steering command value S is changed from S ₁ to S _2, and the steering angles α ₁ , α _{2 of the} respective wheels are changed. , alpha _3, the alpha _4, each steering angle corresponding to the steering command value _{S 1 [α 1, α 2} , α 3, α 4] each steering angle corresponding to the steering command value _{S 2} from _S1 [α _1, α _{2, α 3, α 4]} in the process of transition to _S2, micro transition steering satisfying the steering constraint condition with respect to the steering command value S steering command value obtained by adding a small steering command value [Delta] S to ₁ (S _{1 +} ΔS) Calculate the angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + ΔS,} and perform the minute transition steering Angle _{[α 1, α 2, α} 3, α 4] S1 + ΔS each steering angle alpha _{1 toward, α 2, α 3, α} 4 are changed and the steering angle _{α 1, α 2, α 3} , α 4 Is detected to reach the minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + ΔS} and the steering angle is matched, and then the steering command value (S ₁ + ΔS) is further reduced to the minute steering command value ΔS. Is calculated with respect to the steering command value (S ₁ + 2ΔS) to which a small transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + 2ΔS} that satisfies the steering constraint conditional expression is calculated. ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + 2ΔS} , the steering angles α ₁ , α ₂ , α ₃ , α ₄ are changed, and thereafter the steering angles α ₁ , α ₂ , α ₃ of the respective wheels are similarly changed. , after detecting that the alpha ₄ has aligned steering angle, successively added steering command value small steering command value [Delta] S (S ₁ + Small transition steering angles that satisfy the steering constraint condition expression for _{ΔS) [α 1, α 2} , α 3, α 4] S1 + nΔS computes its small transition steering angles _{[α 1, α 2, α} 3, α ₄ ] Each steering angle α ₁ , α ₂ , α ₃ , α ₄ is changed toward _{S 1 + nΔS} , and each steering angle α ₁ , α ₂ , α ₃ , α ₄ becomes a minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] The detection that the steering angle is matched by reaching _{S1 + nΔS} is repeated, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the respective wheels are changed to the respective steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] A steering control method for a four-wheel independent steering vehicle, wherein the steering angle is changed from _S1 to each steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _S2 . By changing the way of taking the steering command value, the steering angles α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , ₄ of the four wheels of the vehicle according to the steering constraint condition formula that forms a predetermined steering mode. In the steering control in which n ₂ , n ₃ , and n ₄ are individually controlled to change the traveling direction of the vehicle, one variable in the steering constraint conditional expression is set as a steering command value S, and the steering command value S is changed from S ₁ to S ₂ to change the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the wheels from the steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _S1 corresponding to the steering command value S _1. each steering angle corresponding to the command value _{S 2 [α 1, α 2} , α 3, α 4] in the process of transition to _S2, the steering command value _S steering command value obtained by adding a small steering command value ΔS to _{1 (S 1} + [Delta] S) satisfying the steering constraint condition formula [ _1] , [alpha] ₂ , [alpha] ₃ , [alpha] ₄ ] _{S1 + ΔS} and minute transition rotation speed [n ₁ , n ₂ , n ₃ , n ₄ ] _{S1 + ΔS} is calculated, and its minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + ΔS} and its minute transition rotation speed [N ₁ , n ₂ , n ₃ , n ₄ ] Change each steering angle α ₁ , α ₂ , α ₃ , α ₄ and each rotational speed n ₁ , n ₂ , n ₃ , n ₄ toward _{S 1 + ΔS} , After detecting that each steering angle α ₁ , α ₂ , α ₃ , α ₄ has reached the minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + ΔS} and matched the steering angle, the steering is performed. A small transition steering angle [α ₁ , α ₂ , α ₃ , α satisfying the steering constraint condition with respect to a steering command value (S ₁ + 2ΔS) obtained by adding a small steering command value ΔS to the command value (S ₁ + ΔS). ₄ ] _{S1 + 2ΔS} and minute transition rotational speed [n ₁ , n ₂ , n ₃ , n ₄ ] _{S1 + 2 ΔS} is calculated, and the small transition steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + 2ΔS} and the small transition rotational speeds [n ₁ , n ₂ , n ₃ , n ₄ ] _{S1 + 2ΔS} toward each steering angle α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , n ₂ , n ₃ , n ₄ are changed, and thereafter the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the respective wheels are similarly changed. After detecting that the steering angle is matched, the small transition steering angle [α ₁ , α ₂ , α satisfying the steering constraint condition expression with respect to the steering command value (S ₁ + nΔS) obtained by sequentially adding the small steering command value ΔS. ₃ , α ₄ ] _{S1 + nΔS} and the minute transition rotation speed [n ₁ , n ₂ , n ₃ , n ₄ ] _{S1 + nΔS} , and the minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + nΔS} and its micro shift revolution speed _{[n 1, n 2, n} 3, n 4] towards the _{S1 + nΔS} Each steering angle _{α 1, α 2, α 3} , α 4 and changing the respective rotational speed _{n 1, n 2, n 3} , n 4, each steering angle _{α 1, α 2, α 3} , α 4 minute migration Steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{S1 + nΔS} is reached and the detection of the steering angle alignment is repeated, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the respective wheels are respectively set. Steering control of a four-wheel independent steering vehicle characterized by changing the steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _S1 to each steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _S2 . Method. By changing the way of taking the steering command value, the steering angle α1, α2, α3, α4 of the four wheels of the vehicle is individually controlled according to the steering constraint condition formula that forms a predetermined steering mode, thereby changing the traveling direction of the vehicle. In the steering control to be changed, the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc, and the center point with respect to the position of each wheel, that is, the center point of the rectangle whose vertex is the position of each wheel, that is, each wheel position The distance R from the point equidistant to the steering wheel is a steering command value, the steering command value R is changed from R1 to R2, and the steering angles α1, α2, α3, α4 of the wheels are changed to the steering command value R1. Each corresponding steering angle [α1, α2, α3, α4] _R1 To each steering angle [α1, α2, α3, α4] _R2 corresponding to the steering command value _R2 In the process of shifting to the steering command value R1, a small steering angle [α1, α2, α3, α4] _{R1 + ΔR} that satisfies the steering constraint condition with respect to the steering command value (R1 + ΔR) obtained by adding the small steering command value ΔR to the steering command value R1 Calculate and the minute transition steering angle [α1, α2, α3, α4] _{R1 + ΔR} Each steering angle α1, α2, α3, α4 is changed toward the steering angle α1, α2, α3, α4, and the steering angle alignment is achieved by reaching the minute transition steering angle [α1, α2, α3, α4] _{R1 + ΔR.} After detecting that the steering command value (R1 + ΔR) and the steering command value (R1 + 2ΔR) obtained by adding the small steering command value ΔR, the small transition steering angle [α1, α2, α3 satisfying the steering constraint condition formula is satisfied. , _Α4 ] _{R1 + 2ΔR} , and the small steering angle [α1, α2, α3, α4] _{R1 + 2ΔR} Each of the steering angles α1, α2, α3, α4 is changed toward, and thereafter, similarly, after detecting that the steering angles α1, α2, α3, α4 of the wheels are matched to the steering angle, the minute steering command value ΔR is changed. A minute transition steering angle [α1, α2, α3, α4] satisfying the steering constraint condition is calculated with _respect to the sequentially applied steering command value (R1 + nΔR), and _{R1 + nΔR} is calculated, and the minute transition steering angle [α1, α2, α3, α4] is calculated. ] _{R1 + nΔR} The steering angles α1, α2, α3, and α4 are changed toward the same, and the steering angles α1, α2, α3, and α4 reach the minute transition steering angles [α1, α2, α3, α4] _{R1 + nΔR} , and the steering angles are matched. By repeating this detection, the steering angles α1, α2, α3, α4 of the wheels are changed to the steering angles [α1, α2, α3, α4] _{R1, respectively.} To each steering angle [α1, α2, α3, α4] _R2 A steering control method for a four-wheel independent steering vehicle, characterized by comprising: The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. Is L, and the distance between the center line Y between the right wheel and the left wheel and each wheel is W, and the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center with respect to the position of each wheel When the distance between the points is R, the steering restraint conditional expression that forms the predetermined steering mode with the distance R as the steering command value,

The steering control method for a four-wheel independent steering vehicle according to claim 3, wherein the conditional expression is expressed by: The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. Is L, and the distance between the center line Y between the right wheel and the left wheel and each wheel is W, and the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center with respect to the position of each wheel When the distance between the points is R, the steering restraint conditional expression that forms the predetermined steering mode with the distance R as the steering command value,

The steering control method for a four-wheel independent steering vehicle according to claim 3, wherein the conditional expression is expressed by: By changing the method of obtaining the steering command value, the steering angles α1, α2, α3, α4 and the rotational speeds n1, n2, n3, n4 of the four wheels of the vehicle according to the steering constraint condition formula that forms a predetermined steering mode. In the steering control that changes the traveling direction of the vehicle by controlling the vehicle individually, the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel, that is, the position of each wheel The distance R between the center point of the rectangle, i.e., a point equidistant from each wheel position, is used as a steering command value, and the steering command value R is changed from R1 to R2 to change the steering angle α1, α2 of each wheel. , Α3, α4 are the steering angles [α1, α2, α3, α4] _R1 corresponding to the steering command value _R1. In the process of shifting to each steering angle [α1, α2, α3, α4] _R2 corresponding to the steering command value R2, the steering command value (R1 + ΔR) obtained by adding the minute steering command value ΔR to the steering command value R1 is described above. The minute transition steering angle [α1, α2, α3, α4] _{R1 + ΔR} and the minute transition rotational speed [n1, n2, n3, n4] _{R1 + ΔR} that satisfy the steering constraint condition are calculated, and the minute transition steering angle [α1, α2, α3] is calculated. , Α4] _{R1 + ΔR} And its minute transition rotational speed [n1, n2, n3, n4] Each steering angle α1, α2, α3, α4 and each rotational speed n1, n2, n3, n4 are changed toward _{R1 + ΔR} , and each steering angle α1, α2 is changed. , Α3, α4 reach the minute transition steering angle [α1, α2, α3, α4] _{R1 + ΔR} and detect that the steering angle is matched, and then add the minute steering command value ΔR to the steering command value (R1 + ΔR). A small transition steering angle [α1, α2, α3, α4] _{R1 + 2ΔR} and a small transition rotational speed [n1, n2, n3, n4] _{R1 + 2ΔR} that satisfy the steering constraint condition formula with respect to the steering command value (R1 + 2ΔR), The minute transition steering angle [α1, α2, α3, α4] _{R1 + 2ΔR} And its minute transition rotational speed [n1, n2, n3, n4] The steering angles α1, α2, α3, α4 and the rotational speeds n1, n2, n3, n4 are changed toward _{R1 + 2ΔR.} After detecting that the steering angles α1, α2, α3, and α4 of the steering are matched, the small transition steering angle satisfying the steering constraint condition formula with respect to the steering command value (R1 + nΔR) obtained by sequentially adding the small steering command value ΔR [ [alpha] 1, [alpha] 2, [alpha] 3, [alpha] 4] _{R1 +} n [ _Delta ] _R and a minute transition rotational speed [n1, n2, n3, n4] _{R1 +} n [ _Delta ] _R are calculated and the minute transition steering angle [[alpha] 1, [alpha] 2, [alpha] 3, [alpha] 4] _{R1 + n} [ _Delta ] _R And its minute transition rotational speed [n1, n2, n3, n4] Each steering angle α1, α2, α3, α4 and each rotational speed n1, n2, n3, n4 are changed toward _{R1 + nΔR} , and each steering angle α1, α2 is changed. , Α3, α4 have reached a minute transition steering angle [α1, α2, α3, α4] _{R1 + nΔR} is repeatedly detected and the steering angle alignment is repeated, and the steering angles α1, α2, α3, α4 of the respective wheels are respectively steered. Angle [α1, α2, α3, α4] _{R 1} To each steering angle [α1, α2, α3, α4] _{R 2} A steering control method for a four-wheel independent steering vehicle, characterized by comprising: The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α _4, and the rotational speeds for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. N ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each wheel The distance R is the steering command value, where R is the distance between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel. The steering constraint condition formula that forms the predetermined steering mode is

The steering control method for a four-wheel independent steering vehicle according to claim 6, wherein the conditional expression is expressed by: The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α _4, and the rotational speeds for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. N ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each wheel The distance R is the steering command value, where R is the distance between the center point of the concentric arc when the turning trajectory of each wheel is a concentric arc and the center point with respect to the position of each wheel. The steering constraint condition formula that forms the predetermined steering mode is

The steering control method for a four-wheel independent steering vehicle according to claim 6, wherein the conditional expression is expressed by: By changing the method of obtaining the steering command value, the vehicle is controlled by individually controlling the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the four wheels of the vehicle in accordance with a steering constraint conditional expression that forms a predetermined steering mode. in the steering control of changing the running direction of the angle alpha _n formed between the center line Y between the arbitrary point Pn moving direction vehicle right wheels and left wheels on the vehicle as the steering command value, the steering command value alpha _n By changing from α _n1 to α _n2 , the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the wheels are changed to the steering angles [α ₁ , α ₂ , α ₃ , α ₄ corresponding to the steering command value α _n1. ] each steering angle corresponding to the steering command value alpha _n2 from _{αn1 [α 1, α 2,} α 3, in the process of transition to _{α 4]} αn2, steering plus a small steering command value [Delta] [alpha] _n to the steering command value alpha _n1 A small transition steering angle satisfying the steering constraint condition with respect to the command value (α _n1 + Δα _n ) [ _{α 1, α 2, α 3} , calculates the _{α 4]} αn1 ₊ Δαn, the minute migration steering angle _{[α 1, α 2, α} 3, α 4] αn1 + the steering angle alpha ₁ toward the _Δαn, α _2, α ₃ changes the alpha _4, each steering angle _{α 1, α 2, α 3} , α 4 are the small transition steering angles _{[α 1, α 2, α} 3, α 4] αn1 + that matched the steering angle reaches the _Δαn after detecting the steering command value (α _{n1 +} Δα _n) further steering command value obtained by adding a small steering command value _{Δα n (α n1 + 2Δα n} ) small transition steering angles that satisfy the steering constraint condition expression for [ _{α 1, α 2, α 3} , calculates the _{α 4]} αn1 ₊ 2Δαn, the minute migration steering angle _{[α 1, α 2, α} 3, α 4] αn1 + the steering angle alpha ₁ toward the _2Δαn, α _2, α ₃ It changes the alpha _4, similarly hereinafter steering angle alpha ₁ of the wheels, alpha _2, alpha ₃ After the alpha ₄ has detected that the matched steering angle, small transition steering angles [alpha ₁ satisfying the steering constraint condition expression for sequential addition steering command value small steering command value _{Δα n (α n1 + nΔα n} ), α _2, α _3, calculates the _{α 4]} αn1 ₊ nΔαn, the minute migration steering angle _{[α 1, α 2, α} 3, α 4] αn1 + the steering angle alpha ₁ toward the _{nΔαn, α 2, α 3,} α 4 , _And it is repeatedly detected that the steering angles α ₁ , α ₂ , α ₃ , α ₄ reach the minute transition steering angles [α ₁ , α ₂ , α ₃ , α4] _{αn1 + nΔαn and} are matched to the steering angle. , the steering angle alpha ₁ of the wheels, alpha _2, alpha _3, the steering angle alpha ₄ each _{[α 1, α 2, α} 3, α 4] each steering angle from _{αn1 [α 1, α 2,} α 3, α ₄ ] A steering control method for a four-wheel independent steering vehicle, wherein the steering control method is changed to _αn2 . The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. the is L, the distance between the center line Y and the respective wheel between the right wheel and the left wheel and is W, the X-coordinate of an arbitrary point P _n on the vehicle to x _n, the Y-coordinate and y _n, the point Pn When the angle between the movement direction of the vehicle and the center line Y between the right wheel and the left wheel of the vehicle is α _n , the steering constraint condition formula that forms the predetermined steering mode with the angle α _n as the steering command value is

The steering control method for a four-wheel independent steering vehicle according to claim 9, wherein the conditional expression is expressed by: The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. the is L, the distance between the center line Y and the respective wheel between the right wheel and the left wheel and is W, and the X-coordinate of an arbitrary point Pn on the vehicle x _n, the Y-coordinate and y _n, the point Pn When the angle between the moving direction and the center line Y between the right wheel and the left wheel of the vehicle is α _n , the steering constraint conditional expression that forms a predetermined steering mode with the angle α _n as a steering command value is:

The steering control method for a four-wheel independent steering vehicle according to claim 9, wherein the conditional expression is expressed by: By changing the way of taking the steering command value, the steering angles α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , ₄ of the four wheels of the vehicle according to the steering constraint condition formula that forms a predetermined steering mode. In the steering control in which the traveling direction of the vehicle is changed by individually controlling n ₂ , n ₃ , and n ₄ , the angle formed by the movement direction of an arbitrary point Pn on the vehicle with the center line Y between the right wheel and the left wheel of the vehicle α _n is a steering command value, the steering command value α _n is changed from α _n1 to α _n2, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ of each wheel correspond to the steering command value α _n1 . each steering angle _{[α 1, α 2, α} 3, α 4] each steering angle corresponding to the steering command value alpha _n2 from _{αn1 [α 1, α 2,} α 3, α 4] in the process of transition to _Arufaenu2, steering wherein the command value alpha _n1 relative small steering command value [Delta] [alpha] _n the steering command value obtained by adding (α _n1 + Δα _n) Small transition steering angles that satisfy the steering constraint condition expression _{[α 1, α 2, α} 3, α 4] αn1 + Δαn and small shift revolution speed _{[n 1, n 2, n} 3, n 4] calculates a _{αn1 + Δαn,} the minute migration Steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn1 + Δαn} and its minute transition rotational speed [n ₁ , n ₂ , n ₃ , n ₄ ] Each steering angle α ₁ , α ₂ , α ₃ toward _{αn1 + Δαn} , alpha ₄ and changing the respective rotational speed _{n 1, n 2, n 3} , n 4, each steering angle _{α 1, α 2, α 3} , α 4 are the small transition steering angles [α _1, α _2, α _{3, α 4] αn1 +} after detecting that the matched steering angle reaches the _{Derutaarufaenu,} the steering command value (α _n1 + Δα _n) further steering command value obtained by adding a small steering command value _{Δα n (α n1 + 2Δα n} ) Is a small transition steering angle [α ₁ , α ₂ that satisfies the steering constraint condition formula , Α ₃ , α ₄ ] _{αn1 + 2Δαn} and minute transition rotation speed [n ₁ , n ₂ , n ₃ , n ₄ ] _{αn1 + 2Δαn} are calculated, and the minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn1 + 2Δαn} And its minute transition rotational speed [n ₁ , n ₂ , n ₃ , n ₄ ] toward each of the steering angles α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , n ₂ , n ₃ , _{αn1 + 2Δαn} . n ₄ is changed, thereafter Similarly, the steering angle alpha ₁ of the _wheels, alpha _2, alpha _3, after the alpha ₄ has detected that the matched steering angle, successively added steering command value small steering commander value [Delta] [alpha] _n Minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn1 + nΔαn} and minute transition rotational speed [n ₁ , n ₂ , n ₃ , n satisfying the steering constraint condition formula for (α _n1 + nΔα _n ) _4] calculates a _{αn1 + nΔαn,} the minute migration steering angle [alpha _{, Α 2, α 3, α} 4] αn1 + nΔαn its small shift revolution speed _{[n 1, n 2, n} 3, n 4] each steering angle alpha ₁ toward the _{αn1 + nΔαn, α 2, α} 3, and alpha ₄ each The rotational speeds n ₁ , n ₂ , n ₃ , and n ₄ are changed so that the steering angles α ₁ , α ₂ , α ₃ , and α ₄ are minute transition steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn1 + nΔαn} The steering angle α ₁ , α ₂ , α ₃ , α ₄ of each wheel is changed to each steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn 1} To each steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] _{αn 2} . The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α _4, and the rotational speeds for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. N ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each wheel angular distance was is W, forming the X-coordinate of an arbitrary point Pn on the vehicle x _n, the Y-coordinate and y _n, the moving direction of the point Pn is the center line Y between right wheels and left wheels of the vehicle during Where α _n is an angle α _n is a steering command value, and a steering constraint conditional expression that forms a predetermined steering mode is

The steering control method for a four-wheel independent steering vehicle according to claim 12, wherein the conditional expression is expressed by: The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α _4, and the rotational speeds for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. N ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each wheel angular distance was is W, forming the X-coordinate of an arbitrary point Pn on the vehicle x _n, the Y-coordinate and y _n, the moving direction of the point Pn is the center line Y between right wheels and left wheels of the vehicle during Where α _n is an angle α _n is a steering command value, and a steering constraint conditional expression that forms a predetermined steering mode is

The steering control method for a four-wheel independent steering vehicle according to claim 12, wherein the conditional expression is expressed by: By changing the method of obtaining the steering command value, the vehicle is controlled by individually controlling the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the four wheels of the vehicle according to the steering constraint condition formula that forms a predetermined steering mode. In the steering control for changing the traveling direction of the vehicle, the angle α ₀ formed by the moving direction of the midpoint Pn of the straight line connecting the left and right front wheels and the center line Y between the right wheel and the left wheel of the vehicle is used as the steering command value. The value α ₀ is changed from α ₀₁ to α ₀₂ , and the respective steering angles α ₁ , α ₂ , α ₃ , α _{4 correspond} to the steering command value α ₀₁ [α ₁ , α ₂ , α ₃ , α ₄ ] α _In the process of shifting from [ _01] to [[alpha] ₁ , [alpha] ₂ , [alpha] ₃ , [alpha] ₄ ] [alpha] ₀₂ corresponding to the steering command value [alpha] ₀₂ , the steering command value ([alpha] ₀₎ is added to the steering command value [alpha] _01. α ₀₁ + Δα ₀₎ the steering constraint micro transition steering angles that satisfy the expression for [α _1, α _2, α _, Α _4] α01 ₊ Δα0 computes its small transition steering angles _{[α 1, α 2, α} 3, α 4] α01 + Δα0 the steering angle alpha ₁ toward, alpha _2, alpha _3, changing the alpha _4, each After detecting that the steering angles α ₁ , α ₂ , α ₃ , α ₄ have reached the minute transition steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{α01 + Δα0} and matched the steering angle, the steering command value (α ₀₁ + Δα ₀₎ further steering command value obtained by adding a small steering command value _{Δα 0 (α 01 + 2Δα 0} ) small transition steering angles that satisfy the steering constraint condition expression for _{[α 1, α 2, α} 3 , Α ₄ ] _{αn1 + 2Δα0} is calculated, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ are changed toward the small transition steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{α01 + 2Δα0} , and thereafter Similarly, each steering angle alpha ₁ of the _{wheels, α 2, α 3, α} 4 are the steering SumiSei After it is detected that the micro transition steering angles [alpha ₁ satisfying the steering constraint condition expression for sequential addition steering command value small steering command value _{Δα 0 (α 01 + nΔα 0} ), α 2, α 3, calculates the _{α 4]} α01 ₊ nΔα0, the minute migration steering angle _{[α 1, α 2, α} 3, α 4] α01 + nΔα0 the steering angle alpha ₁ toward, α _2, α _3, by changing the alpha _4, each steering Steering of each wheel is repeated by detecting that the angles α ₁ , α ₂ , α ₃ , α ₄ have reached the minute transition steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] _{α01 + nΔα0} and the steering angles are aligned. The angles α ₁ , α ₂ , α ₃ , α ₄ are changed from the steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] α ₀₁ to the steering angles [α ₁ , α ₂ , α ₃ , α ₄ ] α, respectively. A steering control method for a four-wheel independent steering vehicle, wherein the steering control method is changed to ₀₂ . The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. Is L, the distance between the center line Y between the right and left wheels and the distance between each wheel is W, and the moving direction of the midpoint Pn of the straight line connecting the left and right front wheels is between the right and left wheels of the vehicle when the angle between the center line Y and the alpha _0, the angle alpha ₀ and the steering command value, the steering constraint condition equations for forming a prescribed steering mode,

The steering control method for a four-wheel independent steering vehicle according to claim 15, wherein the conditional expression is expressed by: The steering angle for each of the right front wheel, left front wheel, right rear wheel, and left rear wheel is α ₁ , α ₂ , α ₃ , α _4, and the distance between the center line X between the front wheel and the rear wheel and each wheel. Is L, the distance between the center line Y between the right and left wheels and the distance between each wheel is W, and the moving direction of the midpoint P0 of the straight line connecting the left and right front wheels is between the right and left wheels of the vehicle when the angle between the center line Y and the alpha _0, the angle alpha ₀ and the steering command value, the steering constraint condition equations for forming a prescribed steering mode,

The steering control method for a four-wheel independent steering vehicle according to claim 15, wherein the conditional expression is expressed by: By changing the way of taking the steering command value, the steering angles α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , ₄ of the four wheels of the vehicle according to the steering constraint condition formula that forms a predetermined steering mode. In steering control in which n ₂ , n ₃ , and n ₄ are individually controlled to change the traveling direction of the vehicle, the moving direction of the midpoint P0 of the straight line connecting the left and right front wheels is the center line between the right and left wheels of the vehicle. The angle α ₀ formed with Y is set as the steering command value, the steering command value α ₀ is changed from α ₀₁ to α _02, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the respective wheels are changed to the steering command value α. each steering angle corresponding to _{01 [α 1, α 2,} α 3, α 4] each steering angle corresponding to each steering command value alpha ₀₂ from _{α01 [α 1, α 2,} α 3, α 4] goes to _α02 in the course of the steering command value alpha ₀₁ a minute steering commander value [Delta] [alpha] ₀ steering commander value plus (α _{01 +} Δα ₀ The steering micro transition steering angles that satisfy the constraint condition expression _{[α 1, α 2, α} 3, α 4] α01 + Δα0 and small shift revolution speed _{[n 1, n 2, n} 3, n 4] calculates the _{α01 + Δα0} against its small transition steering angles _{[α 1, α 2, α} 3, α 4] α01 + Δα0 its small shift revolution speed _{[n 1, n 2, n} 3, n 4] each steering angle alpha ₁ toward the _{α01 + Δα0,} α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , n ₂ , n ₃ , n ₄ are changed, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ are changed to the minute transition steering angles [α ₁ , alpha _2, alpha _3, after detecting the _{α 4]} αn1 ₊ Δα0 be aligned steering angle to reach the said steering command value (α ₀₁ + Δα ₀₎ to further fine steering command value [Delta] [alpha] ₀ was added a steering command value (alpha ₀₁ + 2Δα ₀₎ small transition steering angles that satisfy the steering constraint condition expression for _{α 1, α 2, α 3} , α 4] α01 + 2Δαn and small shift revolution speed _{[n 1, n 2, n} 3, n 4] calculates the _{α01 + 2Δα0,} the minute migration steering angle _{[α 1, α 2, α} 3 , Α ₄ ] _{α01 + 2Δα0} and its minute transition rotational speed [n ₁ , n ₂ , n ₃ , n ₄ ] toward each of the steering angles α ₁ , α ₂ , α ₃ , α ₄ and the rotational speeds n ₁ , n toward _{α01 + 2Δα0. 2} , n ₃ , n ₄ are changed, and thereafter, similarly, after detecting that the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the respective wheels are matched to the steering angle, the minute steering command value Δα ₀ is sequentially set. Minute transition steering angle [α ₁ , α ₂ , α ₃ , α ₄ ] satisfying the steering constraint condition with respect to the added steering command value (α ₀₁ + nΔα ₀ ) _{α01 + nΔα0} and minute transition rotational speed [n ₁ , n _{2 , n} 3, _n 4] calculates the _{α01 + nΔα0,} the minute migration Steering angle _{[α 1, α 2, α} 3, α 4] α01 + nΔα0 its small shift revolution speed _{[n 1, n 2, n} 3, n 4] each steering angle alpha ₁ toward the _{α01 + nΔα0, α 2, α} 3 , Α ₄ and the rotational speeds n ₁ , n ₂ , n ₃ , n ₄ are changed, and the steering angles α ₁ , α ₂ , α ₃ , α ₄ are changed to the minute transition steering angles [α ₁ , α ₂ , α _3. , Α ₄ ] by repeatedly detecting that the steering angle has been matched by reaching _{α01 + nΔα0} , the steering angles α ₁ , α ₂ , α ₃ , α ₄ of the wheels are set to the steering angles [α ₁ , α ₂ , α _{3, respectively.} , alpha _4] each steering angle from _{α01 [α 1, α 2,} α 3, α 4] 4 -wheel independent steering steering control method for a vehicle, characterized in that changing to _Arufa02. The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α _4, and the rotational speeds for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel, respectively. N ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each wheel When the distance between the left and right wheels is W and the angle between the midpoint P0 of the straight line connecting the left and right front wheels and the center line Y between the right and left wheels of the vehicle is α ₀ , the angle α ₀ is steered The steering restraint conditional expression that forms a predetermined steering mode as a command value is

The steering control method for a four-wheel independent steering vehicle according to claim 18, wherein the conditional expression is expressed by: The steering angles for the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel are α ₁ , α ₂ , α ₃ , and α ₄ respectively, and the rotation is performed for each of the right front wheel, the left front wheel, the right rear wheel, and the left rear wheel The speed is n ₁ , n ₂ , n ₃ , n ₄ , the distance between the center line X between the front wheel and the rear wheel and each wheel is L, the center line Y between the right wheel and the left wheel and each When the distance between the wheels is W and the angle between the moving direction of the midpoint P0 of the straight line connecting the left and right front wheels and the center line Y between the right wheel and the left wheel of the vehicle is α ₀ , the angle α ₀ is Steering restraint conditional expression that forms a predetermined steering mode as a steering command is

The steering control method for a four-wheel independent steering vehicle according to claim 18, wherein the conditional expression is expressed by:   The steering control method for a four-wheel independent steering vehicle according to any one of claims 1 to 20, wherein the number of times the minute steering command value is added to the steering command value is three or less. The predetermined steering mode is a steering mode arbitrarily selected from a plurality of types of steering modes including a forward / reverse mode of the vehicle, and the steering angles α ₁ , α ₂ , α ₃ , α of the wheels when the steering mode is changed. ₄ is reset to the straight traveling direction of α ₁ = α ₂ = α ₃ = α ₄ = 0, and then the respective steering angles α ₁ , α ₂ , α ₃ , α ₄ according to the steering constraint conditional expression forming a predetermined steering mode. The steering control method for a four-wheel independently-steered vehicle according to any one of claims 1 to 21, wherein the steering wheel is changed individually. The predetermined steering mode is a steering mode arbitrarily selected from a plurality of types of steering modes including a forward / reverse mode of the vehicle, and the steering angles α ₁ , α ₂ , α ₃ , α of the wheels when the steering mode is changed. _4, after filling the steering constraint condition after the steering mode is changed, the steering control of a four-wheel independent steering vehicle according to any one of claims 1 to 22, characterized in that driving and moving the vehicle Method.

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